RED SEAL MACHINIST EXAM PREPARATION 2026–2027

Chip conveyors, high-pressure coolant, air blast, and chip-breaking feeds and tool geometry. Long chips can wrap the tool, scratch the finish, or cause a crash, so stop and clear them with a hook only when the machine is stopped.

Two or three flutes for aluminum and other soft materials for chip space, four flutes for general steel work, and five or more flutes for finishing and hard materials, where there are lighter chips and more strength.

On mills feed is normally in inches or mm per minute (G94). On lathes feed is normally per revolution (G99 or G95, depending on the control). F gives the value, and it is modal.

Touch the tool to a known diameter and face, then enter the X and Z values in the geometry offset table. Wear offsets are used for small size corrections, so that geometry offsets are not changed after the setup.

Choose the work datum on the print, convert all dimensions to X, Y and Z values from it, calculate tangent and arc points with trigonometry where they are not given, and check units (inch or metric) before programming.

Z is parallel to the spindle axis, X is the axis of longest travel, and Y completes the right-hand rule. A, B and C are rotary axes about X, Y and Z. On a lathe, Z is along the spindle and X is across the diameter.

I is the distance in X, and J the distance in Y, from the arc start point to the arc center (incremental). Example: a counterclockwise quarter circle from X1.0 Y0 to X0 Y1.0 around the origin is G03 X0 Y1.0 I-1.0 J0.

With the tool at Z0, touch the tool to the part surface or a gauge block, press the measure key to store the position (adjusting for the block height), and verify that the tool reaches the correct position.

Each stores the X, Y and Z distance from machine zero to the part zero. They are set with an edge finder, indicator or probe, and let one program run in several fixtures or let several parts be placed on a table. Extended offsets such as G54.1 P1 add more.

X is normally programmed as a diameter, so an X move of 0.100 in changes the radius by 0.050 in. Z is the position along the spindle, and Z0 is generally set at the finished face of the part.

Servo motors turn ball screws with low backlash, and encoders or linear scales report position to the control. The resolution is commonly 0.0001 in or 0.001 mm. Linear guideways support the table with low friction.

The path is offset from the programmed contour by the D value. For an outside profile, entering a smaller value moves the cutter closer to the part and removes more material, and a larger value moves it away. Use the wear offset for small adjustments.

Positions are given as X, Y and Z distances from a zero point. Movement to the right, away from the operator or up is positive on a vertical mill, and the quadrants are numbered counterclockwise from the positive X and Y quadrant.

Q is the depth of each peck. The drill advances by Q, retracts fully to the R plane to clear the chips, and then rapids back to just above the last depth before the next peck.

Cantilever deflection increases with the cube of the length, so doubling the stickout makes the deflection eight times larger. Use the shortest tool and holder that reach the work.

G04 with P (milliseconds) or X (seconds), depending on the control, such as G04 P500 for half a second. It is used for spot facing, bottoming a hole, and letting the tool clean up the bottom of a cut.

Determine the last good block, make sure the spindle, coolant and modal states are correct, change the tool and check its offset, and use the program restart function or a sequence number to resume. Clear the area of broken pieces first.

Check that the program name and revision match the setup sheet, compare tool numbers, offsets and work zero, review the program for errors, and simulate it graphically. Mistakes in decimal points, tool numbers or work offsets cause crashes.

Measure the part and enter a correction in the wear offset equal to the error in the direction needed. Example: if a diameter is 0.002 in oversize, enter -0.002 in the X wear offset. Do not change the geometry offset.

To set work offsets, measure tool length and diameter, and check part features during the cycle. The probe triggers when it touches the surface and records the position using the macro skip function (G31), which saves time and reduces errors.

Indicate the fixed jaw or locating edge with a dial test indicator to within the tolerance, tighten the bolts, recheck the reading, and then find the work zero. A probe may be used for alignment checks.

G02 or G03 with X, Y and R. R is positive for arcs of 180 degrees or less and negative for arcs over 180 degrees. A full circle cannot be programmed with R, and requires I and J.

Change the spindle speed by 5 to 10 percent, reduce the stickout, reduce the radial engagement, use variable-pitch tools or damped bars, and improve the work holding. Changing speed often moves the cut into a stable zone.

With a refractometer, usually at 5 to 10 percent concentrate for water-soluble coolant. Also check the pH (often 8.5 to 9.5), the odor, tramp oil and the sump cleanliness. Poor coolant harms tools, finish and operator health.

Start it with a linear move that is at least as long as the cutter radius, positioned in open space beside the part, and cancel it with a linear move away from the part. Starting on an arc or inside the part can gouge it.

Time = path length at feed / feed rate, plus rapid moves, tool changes and dwell times. Example: 60 in of cutting at 20 in/min takes 3 minutes. CAM software can provide an estimate.

G02 is clockwise and G03 is counterclockwise, as seen looking down on the plane from the positive side of the third axis (for example, looking down on XY from +Z). The end point is X and Y, and the center is given by I and J or by R.

Feed per minute = rpm x pitch, or rpm / TPI for inch threads. Example: a 1/4-20 tap at 500 rpm needs 500 / 20 = 25 in/min. Rigid tapping synchronizes the spindle and the Z axis.

Reduce the rapid and feed overrides, use single block, keep a hand on feed hold, run with the Z work offset raised for a dry run, then lower the offset and cut. Check the first part against the drawing before running production.

Locate the X and Y edges (or center of a bore), enter the machine coordinates in the G54 offset (adjusting for the tool radius or probe size), and verify with an MDI move to a known point. Z is usually set from the top of the part.

Touch off on the top of the part or a setting block, or use a tool setter or laser. The measured value is entered in the tool length offset (H) register and in the geometry table for lathe tools.

Counting the parts or minutes of each tool, spindle load monitoring, and wear offsets let the control call a sister tool when the life is over. Replacing tools at planned intervals prevents scrap and crashes.

Read the alarm number and message, find its cause in the manual, correct the cause (such as an overtravel limit, servo overload, low lubricant or door open), and then reset. Never clear an alarm repeatedly without finding the cause.

Typical positional tolerances of plus or minus 0.0005 in (0.01 mm) in general production, and plus or minus 0.0002 in or better with care. Finishes of 16 to 63 microinches Ra are typical for milling and turning.

Backlash is lost motion when an axis reverses direction, and pitch error is the deviation of ball screw accuracy along the axis. Controls store compensation values measured by a laser interferometer or ball bar test to correct them.

Short routines for repeated hole-making operations, such as G81 drilling, G82 drilling with dwell (spot facing), G83 peck drilling, G73 high-speed peck drilling, G84 tapping, G85 and G86 boring, and G76 fine boring. They are cancelled with G80.

A wrong or missing tool length offset, wrong work offset, wrong tool called, decimal point errors, a part not clamped, incorrect program modes, and a tool length set with the wrong tool. Prevent them with simulation, dry runs and checking offsets.

Facing, contouring, pocketing, adaptive (high-efficiency) clearing with a constant tool load, drilling and tapping cycles, rest machining, and 3D surfacing with ball end mills. Lead-in arcs and ramp entries are used to reduce tool shock.

Coordinate rotation (G68) turns the programmed shape about a point, scaling (G51) enlarges or reduces it, and mirror image reverses it about an axis. They allow one program to produce rotated or mirrored parts.

Cp = (upper limit - lower limit) / (6 x standard deviation) measures the process spread against the tolerance. Cpk also considers how well the process is centered. A Cpk of 1.33 or higher is generally considered capable.

Programs that use variables (such as #100), arithmetic, and logic (IF, WHILE) to program families of parts, probing routines and calculated positions. A macro reads values from the control and adjusts the program as needed.

M00 stops the program and waits for the operator to press cycle start, which is used for inspections or chip clearing. M01 is an optional stop, which acts only if the optional stop switch is on.

A thread mill is programmed with helical interpolation and one cutter can machine different diameters of the same pitch. It cuts blind holes to the bottom, does not break in the hole like a tap, and works well in hard materials and large threads.

G00 is rapid positioning, G01 is linear interpolation at a programmed feed, G02 is a clockwise arc, G03 is a counterclockwise arc, and G04 is a dwell. Rapid moves are not straight lines at a controlled feed, so they must be programmed clear of the work.

CAT (V-flange, 7:24 taper), BT (similar 7:24 taper with a different flange and retention), and HSK (hollow shank, 1:10 taper with face contact, used for high speed and rigidity). CAT and BT holders are not interchangeable.

Face mills (commonly 45 degree lead), square shoulder mills (90 degree), high-feed mills (thin chip at a shallow lead angle, high feed rates) and round-insert cutters. Choose the cutter by the geometry needed and the machine power.

M00 program stop, M01 optional stop, M02 program end, M03 spindle clockwise, M04 spindle counterclockwise, M05 spindle stop, M06 tool change, M08 coolant on, M09 coolant off, M30 program end and rewind, M98 subprogram call and M99 subprogram return.

Each axis may move at its own rapid rate, so the path is not a straight line and can strike clamps, fixtures or the part. Move to a safe Z height first, and keep the path clear in X and Y.

Vertical machining centers (VMC), horizontal machining centers (HMC), CNC lathes and turning centers, mill-turn machines, 5-axis machining centers, and electrical discharge machines (EDM), both wire and sinker types. CNC also controls grinders, routers and laser or plasma cutters.

Worse finish, burrs, size drift, more noise or vibration, higher spindle load, changes in chip color or shape, and sparks. Change the tool before it breaks or damages the part.

End mills whose flutes are spaced or angled unequally, which breaks up the regular tooth frequency and reduces chatter and vibration, particularly with long stickout or thin walls.

Turret tool mounting systems. VDI uses toolholders with a toothed shank clamped in a turret socket, and BMT uses holders bolted to the turret. Both systems locate the tool accurately and may supply coolant through the holder.

Fine boring heads with micrometer adjustment, rough and finish boring bars, and back-boring tools. Choose a bar with the largest diameter that fits the bore and the shortest length, and use rigid holders.

On Fanuc-style controls: G71 rough turning, G72 rough facing, G73 pattern repeating, G70 finishing, G74 end-face peck drilling, G75 grooving, G76 threading, and G90, G92 and G94 for simple turning, threading and facing cycles. Codes vary between controls.

Check the way and spindle lubricant, coolant level and concentration, air pressure and filters, clean chips from the way covers, table and tool changer, wipe the spindle taper and tool holders, and check the guards, doors and the emergency stop.

Comments are placed in parentheses and are ignored by the control. A slash at the start of a block (block delete) skips the block if the block skip switch is on.

G96 selects constant surface speed, with S in sfpm or m/min, so rpm rises as the diameter decreases. G97 selects a fixed rpm. G50 (on many controls) sets a maximum spindle speed limit to prevent excessive rpm at small diameters.

G is a preparatory function, M is a miscellaneous function, N is a sequence number, X Y Z are axis positions, I J K are arc center distances, R is a radius or return plane, F is feed, S is spindle speed, T is the tool, H is a tool length offset, D is a cutter compensation offset, P is dwell, and Q is a peck depth.

G17, G18 and G19 select the XY, XZ and YZ planes for arcs and cutter compensation. G20 selects inch units and G21 selects metric units.

G43 H## applies the stored tool length so that every tool reaches the same Z position regardless of its length. G49 cancels it. The length is measured by touching off to the part or in a tool presetter.

The work material, the operation (roughing or finishing), machine rigidity and power, the tolerance and surface finish needed, the feature geometry, tool life and the total cost. Use the tool maker's recommended speeds and feeds.

Measure the critical dimensions with micrometers, bore gauges and calipers, or by probing in the machine, at the first piece and at regular intervals, and adjust the wear offsets to keep dimensions within tolerance.

Software that translates CAM toolpaths into the specific G and M code dialect of the machine control, including the right formats, canned cycles and tool change sequences. A wrong post can produce unsafe code.

A document listing the machine, work holding, work zero, tools and holders with their numbers and offsets, speeds and feeds, and operation sequence. It helps the operator set up the job and repeat it later.

A block such as G17 G20 G40 G49 G80 G90 that cancels leftover modes from the previous job, selecting the XY plane, inch units, no cutter compensation, no tool length offset, no canned cycle and absolute positioning.

It starts holes with a short, stiff tip that prevents the drill from walking, and it can also chamfer the hole edge. Choose its angle (90 or 120 degrees) to be equal to or greater than the drill's point angle.

A separate program called with M98 and ended with M99 that returns to the main program. It saves program length for repeated features, patterns, multiple parts or a multi-pass cut, and is often written in incremental mode.

A device that measures the tool length and diameter outside the machine. The offsets are entered at the control while the machine continues to cut, which reduces downtime and the risk of touch-off errors.

G41 offsets the tool to the left of the programmed path and G42 to the right, as seen looking along the direction of travel, and G40 cancels it. G41 gives climb milling with a clockwise spindle. The radius is stored in the D offset.

A circular move in XY with a simultaneous linear move in Z (G02 or G03 with a Z value). It is used for ramping into pockets, milling large holes and thread milling.

Motor-driven tools in the turret that rotate to drill, mill or tap on the part. With the C axis, which indexes the spindle, they allow milling, cross holes and flats in a single setup.

When the radial depth of cut is less than half the cutter diameter, the actual chip thickness is smaller than the programmed feed per tooth, so the feed can be increased. Example: at 10% radial engagement, the feed per tooth can be increased by about 1.67 times.

A program number (such as O1001), a list of blocks (lines) of words, and an end code (M30). Each block may have a sequence number (N), a G code, coordinates, feed, speed, tool and M codes, and ends with an end-of-block character.

A cut tap removes metal and makes chips, and works in most materials. A form tap displaces the metal to form the thread, makes no chips and gives a strong thread in ductile materials, but needs a larger drilled hole, which is given in the tap maker's table.

In absolute mode (G90) every position is measured from the work zero. In incremental mode (G91) each move is measured from the current position. On many lathe controls, U and W are used for incremental X and Z moves.

G98 returns the tool to the initial Z level after each hole, which clears clamps and obstructions. G99 returns only to the R plane just above the part, which saves time.

Machine zero (home or reference point) is a fixed position set by the machine builder. Work zero (program zero) is the point on the part or fixture chosen by the programmer, and its position from machine zero is stored in a work offset such as G54.

Modal codes stay active until replaced by another code in the same group, such as G01 or F. Non-modal codes work only in the block in which they appear, such as G04 and G28. Only one code of a group should appear in a block.

Open-loop control, as with stepper motors, sends commands without feedback and assumes the movement happened. Closed-loop control uses feedback from encoders or scales to compare actual and commanded positions and correct errors.

A sequential changer presents tools in order of the magazine. A random changer finds any tool by its stored pocket number, so the tool numbers do not have to match their pockets. Oversized tools need adjacent pockets left empty.

Check the program by simulation or backplot, then run it with the feed and rapid overrides low, in single block mode, with the Z work offset raised above the part (a Z shift), and the operator's hand on feed hold. Run the first part and verify it.

Create or import the CAD model, define the stock and work zero, choose tools and toolpaths, simulate them, post-process to the machine's G-code, transfer the program to the control, and prove it out on the machine.

The spindle, ball screws and column expand as they warm up, so dimensions drift during the first parts. Warm the machine up, keep the coolant temperature stable, and use probing or offset updates to compensate.

A correction for the radius of the tool tip, which otherwise causes errors on tapers and arcs. G41 and G42 apply it, and the tool tip number (0 to 9) tells the control the orientation of the tip. The radius is stored in the offset table.

Travel limits, spindle power and torque at the planned rpm, the maximum tool length and diameter, the part and fixture envelope with the door and tool changer, and the weight capacity of the table.

The program revision, setup sheet, tool and offset changes, first-article and in-process inspection results, and the quantities produced. This gives traceability and allows the job to be repeated.

Keep the door closed while running, never bypass interlocks, keep clear of the tool changer and moving axes, wear safety glasses and no loose clothing or jewelry, lock out before maintenance, and use proper lifting for heavy fixtures and parts.

Turn the power on, check the air pressure, lubrication and coolant, zero return (home) all axes, warm up the spindle at low rpm for several minutes, and check the tool holders in the magazine. Do not run the spindle at full speed cold.

Flood coolant, through-tool (through-spindle) coolant, high-pressure coolant, mist, minimum-quantity lubrication (MQL) and air blast. Choose the type to match the tool, material and chip control.

Solid carbide and HSS twist drills, indexable-insert drills for larger holes, spot and center drills, and drills with through-tool coolant holes. Through-spindle coolant at 300 to 1000 psi (20 to 70 bar) clears chips from deep holes.

ER collet chucks, side-lock (Weldon) end mill holders, hydraulic and shrink-fit holders, milling chucks, face mill adapters, drill chucks, tapping heads and boring heads. Shrink-fit and hydraulic holders give the best runout and gripping.

Power (hydraulic) chucks with soft or hard jaws, collet chucks, tailstock centers, steady rests and bar feeders. Soft jaws are bored to fit the part, and chuck pressure is set to the part material and wall thickness.

Precision vises, soft jaws, tombstones and fixture plates, grid plates, zero-point clamping systems, vacuum fixtures, rotary tables and 4th-axis units. Good fixturing gives repeatability and allows several parts per setup.

Feed hold pauses the axis motion so the operator can inspect without losing position. Reset stops the program and returns it to the start. Emergency stop cuts power to the drives and is used when someone is in danger or a crash is imminent.

To finish drilled or bored holes to a tight diameter tolerance (about H7) and a smooth finish. Leave 0.005 to 0.015 in of stock, use a matched holder with low runout, and use coolant.

Runout loads each tooth unevenly, which causes poor finish, short tool life and size errors. Holders for high spindle speeds are balanced (for example to G2.5 at operating rpm) to prevent vibration. Keep taper and collets clean.

Too much pressure distorts thin-walled parts, which then spring back out of round after release. Too little pressure allows the part to slip or be thrown out. Follow the chuck maker's limits for rpm and force.

On many controls such as Fanuc, a value entered without a decimal point (X1) is read as the least input increment (0.0001 in or 0.001 mm) instead of 1 inch. Always include the decimal point.

To make sure that no tool, holder or spindle nose can hit the clamps, vise or part when moving. Check clearances in the simulation, and use safe heights and lead-in moves around fixtures.

The drawbar grips the knob to pull the holder into the spindle taper. A wrong thread, angle or length can release the tool during cutting or a tool change, which causes a crash or injury. Check the knobs for wear and tightness.

Face the end, then drill a center hole with a combination drill and countersink, which gives a 60 degree countersink. A bell-type center drill adds a protective 120 degree chamfer. Do not drill so deep that the point bottoms in the hole.

Driver / driven = lead screw TPI / desired TPI. Example: a lathe with an 8 TPI lead screw cutting 16 TPI needs 8 / 16 = 1 / 2, so a 40-tooth driver on the spindle side and an 80-tooth driven gear on the screw.

Select a grooving tool of the correct width, plunge to the specified depth using the cross slide dial, and check the width and diameter with calipers or a groove gauge. Dimensions come from the ring or O-ring standards.

The letters describe the clamping system, insert shape, holder style or approach angle, insert clearance angle, and hand of the tool (R, L or N). Numbers then give the shank size and length, and the insert size.

Use a sharp tool with positive rake and a small nose radius, high speed, light cuts, and good support. Plastics expand with heat and recover after cutting, so let the part cool before measuring.

With form tools, radius tools or by hand-feeding both slides together, and checking the shape with radius gauges or templates. Take light finishing cuts and blend the shape smoothly.

Rough the diameters, then finish the shoulder with a facing cut using a tool that has a side cutting edge angle clear of the shoulder. Use a tool with a nose radius to produce a fillet radius at the inside corner, which reduces stress concentration.

With a taper gauge or ring gauge, a sine bar and indicator, or by measuring the two diameters and the length and calculating the taper. For fit tapers, apply layout dye or Prussian blue lines on the plug and check the contact pattern.

Use soft jaws bored to the diameter or a mandrel, clamp with light pressure over a large area, and take the finishing cut with the same light clamping pressure so the part does not spring back out of round after release.

External threads are checked with a Go/No-Go ring gauge or a thread micrometer, internal threads with a Go/No-Go plug gauge, pitch with a screw pitch gauge, and pitch diameter with the three-wire method. The Go gauge must turn on freely and the No-Go must not.

The theoretical peak-to-valley height is h = f squared / (8 x r). Example: f = 0.005 in/rev, r = 1/32 in gives h = 0.000025 / 0.25 = 0.0001 in. A larger radius or lower feed gives a better finish.

Levers are set to the position shown on the chart for the required thread pitch or feed, and the gearbox drives the lead screw or feed rod. Change positions with the spindle stopped or turning slowly, and rotate the chuck by hand if the gears do not mesh.

The dial's gear rides on the lead screw. For a thread with an even number of threads per inch, the half-nuts can close at any line, and for an odd number of threads per inch close them on a numbered line. Follow the chart on the lathe for fractions and metric threads.

As a rule of thumb, about 3 times the diameter. Longer work should be supported with a live center or a steady rest to avoid deflection, chatter and the work being thrown out.

Turn the tool at an angle with the compound rest, or use a chamfering tool, and set the chamfer to the size on the drawing, commonly 45 degrees. Chamfer the ends to remove burrs and protect threads.

Drill and bore the through hole, then bore the larger diameter to the required depth with a boring bar or counterbore tool. Use the carriage stop or dial to set depth and square the bottom with a facing motion.

Rough bore, leaving about 0.010 in for finishing, then take a finish cut and a spring pass. Use the shortest, stiffest bar, check the size with a telescoping gauge and micrometer, and finish with the correct tool nose radius.

Face the end, center drill, then drill with the drill held in the tailstock chuck or taper. The work turns and the drill is fed by the quill. Withdraw often to clear chips, lubricate, and use the quill scale to track depth.

Drill undersize (leaving 0.005 to 0.015 in), then ream at about half the drilling speed with a feed of two to three times the drilling feed. Use cutting fluid and a floating reamer holder if there is any misalignment.

Place a precision level across the bed ways at both ends and along the bed, adjust the feet or shims until it reads level, and then confirm with a test cut. A taper along a long turned bar shows twist in the bed.

Select the thread pitch on the quick-change gearbox, and set the compound rest to 29 or 30 degrees. Square the 60 degree threading tool to the work with a center (fishtail) gauge, and use the threading dial to re-engage the half-nuts.

Take a light cut on a bar held in a chuck or between centers, turn collars near each end, and measure them. If the diameters differ, the headstock or tailstock is out of alignment, the ways are worn or the setup deflects.

Reverse the direction of the lead screw so the carriage travels toward the tailstock, or cut from the headstock side to the free end. The tool is started at the left and cuts toward the free end with the spindle running forward.

Set it exactly on center, square to the work, with minimum overhang and a rigid tool post. Use a reduced spindle speed, a steady feed, and cutting fluid. Part off close to the chuck jaws.

Turn a true bearing surface on the work near the center, clamp the steady rest to the bed ways, adjust the three fingers until they touch the work lightly with the work running true, lock them, and keep the contact points oiled.

NPT has a 60 degree thread form and a taper of 1:16 on the diameter (3/4 in per foot), which is a half angle of about 1 degree 47 minutes. Cut it with the taper attachment or tailstock offset, set the thread tool square, and check the fit with a thread gauge or a mating fitting. Thread height is 0.8 x pitch.

Keep the half-nuts engaged if possible. If they were opened, re-engage at the correct line on the thread dial, then bring the tool into the existing groove using the cross slide and compound until it lines up.

Use a sharp tool with a polished positive rake face, high speeds, free chip clearance, and cutting fluid or lubricant to prevent a built-up edge. Chips are long, so use a chipbreaker.

Turn the stock to the major diameter, chamfer the end, set the gearbox and the compound angle, align the tool with the center gauge, and take successive passes with the compound while engaging the half-nuts at the thread dial. Check with a gauge or mating nut.

Bore to the minor diameter, cut a relief groove at the end of the thread if needed, and use an internal threading boring bar. For unified threads the basic minor diameter is the major diameter minus 1.0825 x pitch. Example for 1/2-13: 0.5000 - 0.0833 = about 0.4167 in.

Use a tool with zero or slightly negative rake so it does not dig in or grab, run at high speeds and light cuts, and cut dry or with a light oil. Free-cutting brass makes small, easily cleared chips.

Cut dry, with a depth of cut that is deeper than the hard outer scale, using carbide of the K group or similar. Gray iron makes powdery chips, so use dust control or a vacuum and keep it away from the ways.

Mount a dial indicator on a stand and rotate the work, reading total indicator reading (TIR). A TIR of 0.002 in means the surface is eccentric by 0.001 in. Check between centers or in the chuck.

Offset the work in a four-jaw chuck or turn between offset centers, then turn the diameter. For an offset of e, the dial indicator shows a total indicator reading of 2e. Balance the setup for safe running.

Set the knurling tool on center at right angles to the work, use a slow speed with plenty of oil, press firmly to form the pattern, and then feed along the work. The diameter grows slightly after knurling, so turn the stock to the specified size first.

Use the carriage stop or a dial indicator on the carriage, a micrometer stop or a digital readout, and measure from the face datum with calipers or a depth micrometer. Allow for finishing stock before reaching final length.

Support it with a steady rest or a follower rest, take light cuts with a sharp tool with a small nose radius, and use a 90 degree approach angle to reduce radial force. Turn from the tailstock end toward the headstock where possible.

Time = length of cut / (feed per revolution x rpm). Example: a 6 in cut at 0.010 in/rev and 500 rpm takes 6 / (0.010 x 500) = 1.2 minutes.

Use a sharp tool of the right width on center, a reduced speed, and a steady, continuous feed with cutting fluid. Do not let the tool dwell or ride in the cut, and support long overhanging parts to prevent them falling.

Use sharp positive-rake tools or coated carbide, a rigid setup, a steady and positive feed that never dwells, a moderate speed, and ample cutting fluid. Dwelling or light cuts work harden the surface.

Taper per inch = (D - d) / L. The compound angle (half angle) is found from tan(angle) = (D - d) / (2L). Example: D = 1.5 in, d = 1.0 in over 4 in gives tan(angle) = 0.5 / 8 = 0.0625, so the angle is 3.58 degrees.

C is an 80 degree diamond shape, N is 0 degree clearance, M is the tolerance class, and G is a hole with a chipbreaker. 4 is a 1/2 in inscribed circle, 3 is 3/16 in thick, and 2 is a 1/32 in nose radius.

Each dial graduation moves the tool in by the stated amount. On most lathes a 0.001 in change on the dial reduces the diameter by 0.002 in, since the tool takes material from both sides. Remove the backlash by always approaching from the same direction.

Compare the tool tip with the tailstock center point, or face a short test piece and check for a nub. A tool above or below center changes the effective rake and clearance. A parting tool must be exactly on center.

rpm = (cutting speed in sfpm x 4) / diameter in inches. Example: turning a 2 in diameter bar at 90 sfpm gives 90 x 4 / 2 = 180 rpm. For metric, rpm = cutting speed (m/min) x 1000 / (pi x diameter in mm).

MRR (in cubed per min) = 12 x depth of cut x feed (in per rev) x cutting speed (sfpm). Example: 12 x 0.100 x 0.010 x 100 = 1.2 in cubed per minute.

By the swing (the largest diameter that can rotate over the bed) and the distance between centers (the maximum length that can be held between centers). The swing over the cross slide is smaller than the swing over the bed.

Use a test bar between centers with a dial indicator along its length, align the centers by eye to the witness marks, or take trial cuts at each end of a bar and compare diameters. Adjust the set-over screws until the readings match.

Offset = (D - d) / 2 x (total length / length of taper). Example: a taper from 1.25 in to 1.00 in over 5 in of a 10 in bar needs an offset of 0.125 x (10 / 5) = 0.250 in.

M = E + 3W - 0.866P for a 60 degree thread, where E is the pitch diameter, W the wire diameter and P the pitch. The best wire size is 0.57735 x P. Example for 1/2-13 UNC: W = 0.0444, E = 0.4500, so M = about 0.5166 in.

A lathe dog is clamped on the work and driven by a drive plate or by a driving pin in the faceplate. A face driver may be used for work without a dog. Lubricate the dead center.

Rough-center with chalk or the concentric rings, then adjust the jaws while reading a dial indicator, until the total indicator reading is within the required tolerance, often 0.001 in or less. Tighten the jaws evenly after truing.

The compound travel for the full depth = thread depth / cos(29 degrees), about 1.14 times the radial depth. Example for 1/4-20, depth 0.0325 in: the compound is advanced about 0.0372 in in total.

Typically 0.010 to 0.020 in (0.25 to 0.5 mm) for turning finishes, 0.005 to 0.015 in for reaming, and 0.010 to 0.020 in on the diameter for grinding. Allow more for parts that will be heat treated.

Use a chip breaker or a feed that breaks chips, remove chips only with a hook or brush when the spindle is stopped, and never clear stringers by hand. Hot, sharp chips can cause serious cuts and burns.

Flood the tool tip at the point of cutting with a steady stream. For carbide, flood continuously or run dry. Intermittent application causes thermal shock and cracks in the insert.

Hold a strip of emery cloth or a polishing stick against the work with the tool post clear, keep fingers away from the work, and never wrap abrasive cloth around the work or your fingers. Use a moderate speed.

Aluminum or steel jaws that are bored or turned on the lathe to the diameter of the part at the same clamping pressure as used for the job. They grip finished or thin parts without marking, and give a concentric hold.

5C collets hold round, square and hex stock accurately with low runout, and ER collets clamp a small range of sizes below the nominal size. Collets give fast, concentric gripping on bar stock and finished parts.

Causes include excessive tool or work overhang, loose gibs or work, a worn tool, too high a speed, a large nose radius and a weak setup. Cures: reduce overhang, add support such as a steady rest, adjust the speed or feed, use a sharper tool or a smaller nose radius.

Excessive speed or feed, a tool that is not rigid, running with too little coolant, a poor setup or interrupted cuts, tool materials unsuited to the work, a dull edge, and chips packed around the tool.

High-speed steel (HSS and cobalt HSS), carbide (uncoated and coated with TiN, TiCN, Al2O3 or TiAlN), cermet, ceramic, cubic boron nitride (CBN) and polycrystalline diamond (PCD). Hardness and heat resistance increase from HSS to CBN and PCD, while toughness decreases.

C is an 80 degree diamond, D is a 55 degree diamond, T is a triangle (60 degrees), S is a square (90 degrees), V is a 35 degree diamond, W is a trigon (80 degrees) and R is round. Smaller included angles have weaker corners but access tight areas.

For unified threads the thread depth is 0.6495 x pitch, so for 1/4-20 the depth is 0.6495 / 20 = 0.0325 in. For ISO metric external threads the depth is 0.6134 x pitch.

P (blue) is steel, M (yellow) is stainless steel, K (red) is cast iron, N (green) is non-ferrous metals, S (brown) is heat-resistant alloys and titanium, and H (grey) is hardened materials.

Straight and diamond (crisscross) patterns, in coarse (14 TPI), medium (21 TPI) and fine (33 TPI) pitches. Set the knurling tool at center height, use a slow speed, a feed of about 0.010 to 0.020 in/rev, and plenty of oil.

Three-jaw self-centering chuck, four-jaw independent chuck, collet chucks, faceplates, mandrels, drive plates and centers, and steady and follower rests.

The bed, headstock with spindle, tailstock, carriage (saddle, apron, cross slide, compound rest and tool post), quick-change gearbox, lead screw and feed rod. The apron houses the feed and threading controls.

Flank wear on the relief face (abrasion, limited to about 0.3 mm), crater wear on the rake face (heat and diffusion), built-up edge (workpiece material welded to the edge), notch wear at the depth of cut line, and chipping or thermal cracking.

Compound rest set to half the included angle (short steep tapers), tailstock offset (long gentle tapers between centers), taper attachment (long tapers with a bore or external work), and form tools. CNC lathes interpolate tapers directly.

Use a file with a handle, hold the handle in the left hand, keep the right hand and sleeves clear of the chuck, use a moderate speed and light, steady strokes, and move the tool post out of the way.

Remove the chuck key, tighten the tool post and work holding, use guards, wear safety glasses, tie back long hair, and keep sleeves, jewelry and gloves away from the work. Never use a file without a handle or hold rags against the rotating work.

Roughing uses about 0.010 to 0.020 in per revolution with a heavy depth of cut, and finishing uses about 0.002 to 0.005 in per revolution with a light cut of 0.005 to 0.020 in. Use the heaviest cuts the machine and the setup can support.

As a general guide, about 8 to 14 degrees of rake and 6 to 10 degrees of relief. Softer materials such as aluminum take more rake, and harder materials need less rake and a stronger edge.

With HSS tools: aluminum 200 to 300 sfpm, brass 150 to 300, mild steel 90 to 100, cast iron 60 to 80, stainless steel 50 to 80. With coated carbide, steel is typically about 300 to 600 sfpm and aluminum 1000 or more.

A dull or chipped tool, a built-up edge, feed that is too high, a speed that is too low, a tool that is off center, a loose setup, or insufficient coolant. Remedy by changing the tool, raising the speed or reducing the feed.

A dull tool or one not on center gives torn threads, too much infeed gives wide or rough threads, a missed engagement gives a double thread, an incorrect gearbox setting gives the wrong pitch, and too little depth gives a tight fit.

A contact of about 75% or more along the length of the taper, with the contact heaviest at the large end. Check with Prussian blue and adjust the taper by small changes of the compound or tailstock.

A reduced speed of about one quarter to one half of normal turning speed with HSS tools. Slower speeds give time to disengage the half-nuts at the end of each pass, and carbide threading inserts can run faster.

They curl and break the chip into short pieces, which prevents long stringers that tangle on the work or injure the operator. The type of chipbreaker is chosen for finishing, medium or roughing cuts and the work material.

Back rake and side rake control the chip flow and cutting force, end relief and side relief prevent rubbing of the heel and flank, the side cutting edge angle controls approach, and the end cutting edge angle clears the finished surface. Nose radius strengthens the tip and affects finish.

6g is the common medium tolerance for external threads, and 6H is the common medium tolerance for internal threads. The number is the tolerance grade, and the letter is the position (fundamental deviation).

A is an external thread and B is an internal thread. Class 1 is a loose fit, class 2 is the standard commercial fit, and class 3 is a close fit. Class 2A has an allowance for a clearance, while 3A has none.

Face one end, center drill, rough turn the diameters, drill and bore, thread, finish turn, then flip the part and face to length. Use soft jaws on finished diameters and finish bore and outside diameter in a single setup for concentricity.

A final pass at the same setting, with no added infeed, which removes the slight cutting spring of the tool and work and gives a clean, accurate thread form.

A groove cut at the end of the threaded section, slightly deeper than the thread depth. It gives the tool a place to stop and allows a nut or mating part to run fully to the shoulder.

A short scratch cut near the end of the work, taken before the full cut. Stop the spindle without moving the cross slide, measure the diameter, and adjust the cross slide dial from the result to reach the final size.

Lock the carriage, set the tool on center, and feed the cross slide across the end of the work, either from the outside toward the center or from the center out. Take a light finishing cut at the end. Face first to establish the datum for lengths.

Use the largest bar that fits the bore, hold it with minimum overhang (steel bars to about 4 times the diameter, carbide bars to about 6 times), set the cutting edge on center, and check there is clearance behind the cutting edge.

A live center has bearings and turns with the work. A dead center is hardened, does not turn, and the work rotates on it, so the center hole must be lubricated and the tailstock set to avoid heating. A half center allows facing near the center.

Positive inserts cut with lower force and heat, suit light cuts, soft or gummy materials and slender work, but have a weaker edge. Negative inserts are stronger, have twice as many cutting edges because both sides can be used, and are better for heavy and interrupted cuts.

A steady rest supports a long or slender workpiece at a fixed position on the bed and is used for boring, threading and facing the ends. A follower rest is carried on the carriage and follows the cutting tool, supporting the work against tool pressure.

Wipe and clean chips from the ways and slides, oil the ways, cross slide and compound as the lubrication chart requires, check the oil levels and coolant, and look at guards and the chuck. Avoid cleaning with compressed air, which blows chips into the ways and bearings.

Rough with a heavy depth of cut and feed, leaving about 0.010 to 0.020 in (0.25 to 0.5 mm) of stock, then take a light finishing cut with a lower feed and a higher speed. Measure and make a final cut without changing the tool setting.

Telescoping gauges with an outside micrometer, inside micrometers, dial bore gauges, small hole gauges and go/no-go plug gauges. Check at several depths and angles for taper and out-of-round.

Lock out the machine, clean the mating surfaces, support the chuck on a board over the bed when lifting, and make sure camlocks are fully engaged within the marks. Never leave the chuck key in the chuck.

With a sound setup, about plus or minus 0.001 in is routine, and plus or minus 0.0005 in is possible with care. Finishes of 63 to 125 microinches Ra are typical, and finer finishes require light cuts and a sharp tool.

Threaded noses, D1 camlock noses, and long-taper key-drive noses. Camlock chucks are secured with cam studs, and the cam lock lines must sit within the mark on each stud when properly tightened.

Round (American) tool posts with a rocker, four-way turret tool posts, and quick-change tool posts such as wedge and piston types. A quick-change post speeds up tool changes and repeatability.

Solid (tapered) mandrels press into the bore, expanding mandrels clamp in the bore with a split sleeve, and gang mandrels hold several parts. They allow the outside surface to be turned concentric with a finished bore.

The feed rod drives the carriage through the apron feed clutch for turning and facing. The lead screw and the half-nuts are used only for threading. The two feed systems must never be engaged at the same time.

Only when the spindle has completely stopped on geared-head lathes, and as the operating manual allows on variable-speed lathes. Never stop the chuck with your hand.

For large, flat or irregular work that cannot be held in a chuck. The work is bolted or clamped to the plate, and counterweights must balance it before it is turned.

For square, rectangular and irregular work and for round work that must run true to a very close tolerance. Each jaw is adjusted separately and the work is trued with a dial indicator.

If the tool is above or below center, a small nub or pip is left at the center of the face, and the cutting angles change. Check it against the tailstock center before facing.

Take the first cut deeper than the scale, since the scale is abrasive and dulls the cutter. Use a rigid setup and a carbide cutter or other tough tooling, and avoid cutting the scale with a light pass.

Use a chamfer mill or a 90 degree spot drill, set the depth from the edge, and cut around the edge. Breaking edges by 0.010 to 0.020 in removes burrs and sharp corners.

Use coolant flood or an air blast to clear chips from the cut, brush or vacuum chips after the machine stops, and never use your hand. Compressed air should not be aimed at people or into the ways.

Drill the through hole, then use an end mill, a counterbore tool with a pilot, or a countersink to produce the larger diameter or cone. Control the depth with the quill stop or the knee.

Cut in several axial steps (stepdowns), usually no more than about the cutter diameter per pass, use cutters with enough flute length but no more, and clear chips with air or coolant. Deep pockets need extra rigidity.

Deburr them first, let them reach room temperature, and use micrometers, calipers, depth gauges, height gauges on a surface plate, bore gauges and gauge pins. Use the tool that is ten times more precise than the tolerance.

Tighten the gib adjusting screw until the slide moves smoothly without play or binding. Backlash in the table screws is measured at the handwheel and adjusted at the nut, and a worn screw can be compensated for by always approaching from the same direction.

A typical inch dial has 100 divisions of 0.001 in with one turn moving 0.100 in. Metric dials commonly read 0.02 mm per division. Always approach the final reading from the same direction to avoid backlash errors.

Locate the datum with an edge finder, move to the coordinates with the DRO or dials, spot drill, then drill and finish by reaming or boring. Mating parts can be matched using a transfer punch through the first part.

Cutters come in a set of eight numbered by tooth count range: No. 1 cuts 135 teeth to a rack, No. 2 cuts 55 to 134, No. 3 cuts 35 to 54, No. 4 cuts 26 to 34, No. 5 cuts 21 to 25, No. 6 cuts 17 to 20, No. 7 cuts 14 to 16, and No. 8 cuts 12 to 13. The cutter must match the diametral pitch.

Place the work on clean parallels with the surface to be cut above the jaws, clamp it, and tap it down with a soft hammer until the parallels are tight to the work and cannot be moved by hand. Keep the work and vise clean of chips.

Use sharp polished cutters, high speeds and moderate feeds, air or mist cooling, and light clamping. Heat melts or gums some plastics, and over-tightening distorts parts.

Use stops, locating pins or soft jaws so each part is seated in the same position, clamp with the same force, and check the first part and every nth part against the print.

rpm = (cutting speed x 4) / cutter diameter, and feed (in/min) = rpm x chip load per tooth x number of teeth. Example: a 1/2 in, 4-flute HSS cutter at 90 sfpm runs 720 rpm and at 0.002 in per tooth feeds 720 x 0.002 x 4 = 5.76 in/min.

Use a machinist's square and a feeler gauge, a dial test indicator on a surface plate, or measure with a micrometer at several points. Equal readings at four corners show the faces are parallel.

Mount the block vertically in the vise with support, or place it flat on parallels and use the side of an end mill or a face mill. Use a stop for repeat parts and check the length with calipers or a micrometer, with extra stock for the finishing cut.

x = R cos(angle) and y = R sin(angle), with angle = n x 360 / N. Example: six holes on a 3.0 in circle (R = 1.5) are at (1.500, 0), (0.750, 1.299), (-0.750, 1.299), (-1.500, 0), (-0.750, -1.299) and (0.750, -1.299).

Use light clamping pressure, support the work under the cut, use toe clamps, double-sided tape, or vacuum fixtures where suitable, take light cuts with sharp cutters, and relieve stresses with roughing before the finishing cuts.

Inspect the cutting edges and the end for wear, chips and rounding, and resharpen on a tool and cutter grinder to restore the primary and secondary clearance angles. Carbide cutters are resharpened with a diamond wheel.

Tap by hand with the spindle turned by hand and a tap guide, use a tapping head, or on CNC machines use thread milling cutters. A thread mill produces a thread without the risk of a broken tap and can cut different diameters of the same pitch.

HSS cutters are tougher, cheaper and tolerate lower rigidity, but run at lower speeds. Carbide cutters run two to four times faster and hold an edge longer, but are brittle and require a rigid machine and a setup without vibration.

A worm and gear drive rotates the table. With a 90:1 ratio, one turn of the handwheel is 4 degrees (72:1 gives 5 degrees, 360:1 gives 1 degree). It is used for arcs, circles, bolt circles and indexing, and is centered on the spindle before use.

Mill one face as a datum. Put it against the fixed jaw with a round bar at the movable jaw and mill the adjacent face. Then mill the third face with the first face down on parallels, check squareness, and finish the ends in the same way. Keep to the same reference faces.

The head holds a boring bar and has a micrometer dial for adjustments. Drill or rough bore the hole first, set the cutter to a small cut, and measure the hole. Check whether the dial reads on the radius or the diameter before adjusting.

Lock out the machine, clean the collet and spindle taper, insert the collet with its keyway aligned with the spindle key, tighten the drawbar by hand, insert the cutter fully, then tighten with a wrench. Do not over-tighten.

It shows absolute positions from a set zero, or incremental positions relative to the last move. Set the work zero at the part datum, and use the readout in place of dial graduations. Check it against the dial or calipers when starting a job.

Rough the slot with an end mill, cut the angled faces with a dovetail cutter (commonly 45 or 60 degrees), and check the width over precision pins or rollers. Take light cuts, as the dovetail cutter is weak at the corner.

Choose a cutter diameter of about 1.25 to 1.5 times the width of the cut, and position it so about two-thirds of its diameter engages the work. A cutter exactly centered on the work causes poor chip clearance and a burr on exit.

The depth of the flat is h = R - square root of (R squared - (w / 2) squared), where w is the width of the flat. Example: a 1.000 in shaft with a 0.800 in wide flat has h = 0.5 - square root of (0.25 - 0.16) = 0.2 in. Hold the shaft in a V-block or collet.

Drill or pre-bore the hole, set the boring tool, take a trial cut about 0.010 in deep, measure the bore, and adjust the head by the amount remaining. Make a spring pass on the final cut. Remember that the dial may read radius or diameter.

Fit the arbor in the spindle and secure it with the drawbar, place the spacers and cutters with the keys on the arbor with the cutter near the spindle, install the arbor support, and then tighten the arbor nut. Rotate the cutter in the direction that suits its teeth.

Use an end mill with the diameter equal to the keyway width, center the cutter on the shaft axis using an edge finder or indicator, and cut to the depth in the key table, which is about half the key height. Hold the shaft in a V-block or vise and mill along it for a keyseat.

Mount a dial test indicator on the spindle or a stand, sweep it along the edge of the work, and tap the part until the indicator reading is constant within the tolerance. Then clamp the work.

Spot or drill a starting hole, or ramp in with a helical or sloped entry with a center-cutting end mill, rough the pocket leaving 0.010 in, and then finish the walls and the floor. Make sure chips are cleared from the pocket.

Rough just outside the line, leaving 0.010 to 0.030 in, then finish with a smaller cut and a spring pass. Use a sharp cutter, take light radial cuts, and blend the corners smoothly.

Raise one end by a gauge block stack of height H = L x sin(angle), where L is the roll center distance. Example: a 5 in sine plate set to 20 degrees needs 5 x 0.3420 = 1.710 in of gauge blocks.

Mount it on an arbor, use a slower feed and a reduced speed, support the work well, and apply coolant. Slitting saws are thin and break easily, so avoid side loading.

Use a two-flute center-cutting end mill, usually slightly smaller than the slot width when a precision slot is required, take shallow passes at reduced feed, and finish the width in a second pass. Slots often cut oversize if the cutter has runout.

Turn and bore the gear blank to the outside diameter, mount it on an arbor between the dividing head and tailstock, center the cutter on the blank, touch off at the outside diameter, cut to the whole depth, index for each tooth, and check the tooth thickness with a gear tooth vernier.

Use the side of an end mill or a shell mill, rough leaving about 0.010 in, and finish the wall and the floor with light cuts. The cutter's corner radius defines the radius in the corner.

First cut a plain slot with an end mill to the stem width and the depth of the T. Then use a T-slot cutter at a reduced feed with coolant, taking care that chips clear from the slot.

Clamp a dial indicator in the spindle and sweep the fixed jaw along the table, adjust the vise until the reading is within about 0.001 in across the jaw length (0.0005 in for precision work), then lock the vise.

Use a Woodruff keyseat cutter of the key size, center it on the shaft, and feed it in radially to the specified depth. The seat takes the shape of the cutter, and its depth is checked with a micrometer and gauge.

Use two- or three-flute cutters with polished flutes and a high helix, high spindle speed, good chip clearance and lubricant to prevent a built-up edge. Sharp tools give the best finish.

Tilt the vertical head to the required angle, set the work on an angled vise or sine plate, or use an angle plate. Another option is to use an angle cutter. Check the angle with a protractor or sine bar.

Center the table under the spindle with an indicator, set the cutter offset equal to the arc radius plus or minus the cutter radius, and rotate the table slowly by hand. Keep the feed steady to avoid marking the arc.

A mechanical edge finder has a 0.200 in tip. Spin it at 800 to 1000 rpm and touch it to the edge until the tip steps off and runs true. The spindle center is then 0.100 in from the edge. Electronic edge finders signal contact with a light or buzzer.

One turn of the crank equals 9 degrees, so the crank turns = angle / 9. Example: 27 degrees = 3 turns, and 15 degrees = 1 2/3 turns, or 1 turn plus 12 holes on an 18-hole circle.

Cut dry or use air to clear chips, cut below the hard scale, use abrasion-resistant carbide, and watch the exit of the cut where the edge can break out. Gray iron chips are abrasive, so protect the machine's ways.

Reduce the feed near the exit, cut from the edges toward the center, chamfer the edge first, or back the work with a sacrificial block. A sharp cutter reduces burrs.

MRR (in cubed per min) = width of cut x depth of cut x feed rate. Power at the cutter = MRR x the unit horsepower for the material, about 1.0 for mild steel and 0.3 for aluminum. Example: 1.5 x 0.1 x 12 = 1.8 in cubed per min, or about 1.8 hp for mild steel.

Set the feed rate in inches per minute, adjust the limit stops or trip dogs to stop the table before it hits the end of the cut, and lock the other axes. Disengage the feed before changing direction.

In V-blocks with clamps, in a collet or a three-jaw chuck on the rotary table, in a vise with V-jaws, or between centers on a dividing head. Round work must be prevented from rolling and from turning in the cutter.

For a 40:1 head, index crank turns = 40 / N. Example: 6 divisions need 40 / 6 = 6 2/3 turns, which is 6 full turns plus 12 holes on an 18-hole circle.

Use rigid setups, sharp coated carbide or cobalt cutters, a steady feed that is high enough to avoid rubbing, a moderate speed, and ample coolant. Never let the cutter dwell, since the surface work hardens.

Mount a dial test indicator in the spindle, bring the tip against the bore wall, and sweep it around by hand. Adjust the X and Y positions until the reading stays constant, then zero the DRO. The indicator center is then the center of the bore.

Feed per tooth = table feed (in/min) / (rpm x number of teeth). Example: 24 in/min at 800 rpm with a 6-tooth cutter gives 24 / 4800 = 0.005 in per tooth.

Lead = pi x diameter / tan(helix angle). Example: a 2 in diameter with a 30 degree helix has a lead of 6.2832 / 0.5774 = about 10.88 in. It is used for gearing a dividing head to cut helical flutes and gears.

c squared = a squared + b squared. Example: two holes 3.0 in apart in X and 4.0 in apart in Y are 5.0 in apart on a straight line, since the square root of (9 + 16) is 5.

Feed (in/min) = rpm x feed per tooth x number of inserts. Example: a 6-insert face mill at 500 rpm and 0.006 in per tooth feeds 500 x 0.006 x 6 = 18 in/min.

Lower the rotating or stopped cutter until it just grips a piece of paper or a feeler gauge on the work, then retract and set the Z reading to zero, allowing for the thickness of the paper or feeler (commonly 0.002 to 0.003 in).

Gang milling uses several cutters on one arbor to cut several surfaces at once. Straddle milling uses two side cutters separated by spacers to cut two parallel faces at the same time.

sin(angle) = opposite / hypotenuse, cos(angle) = adjacent / hypotenuse, and tan(angle) = opposite / adjacent. They are used to calculate angles, offsets and hole positions from a drawing.

Pitch diameter = N / DP, outside diameter = (N + 2) / DP, addendum = 1 / DP, whole depth = about 2.157 / DP, and circular pitch = pi / DP. Example: 24 teeth at 8 DP has a pitch diameter of 3.000 in, an outside diameter of 3.250 in, and a whole depth of 0.2696 in.

Excessive feed, packed chips, deflection from a long stick-out, plunging with a non-center-cutting cutter, runout, a dull cutter and hard spots. Dwelling or stopping the spindle in the cut also breaks cutters.

End mills (2-, 3- and 4-flute), ball nose and bull nose, roughing (hog), shell and face mills, fly cutters, slitting saws, side and face cutters, keyseat cutters, T-slot and dovetail cutters, angle and form cutters.

For roughing with an end mill, use an axial depth up to about 1 to 1.5 times the diameter at a reduced radial width, but limit full-width slots to about half the diameter per pass. Leave 0.005 to 0.015 in for the finishing pass.

No gloves, rings or loose clothing, wear safety glasses, secure the work and the cutter, and stop the spindle before measuring, changing tools or cleaning. Keep hands clear of the cutter, remove the wrench or drawbar, and know where the emergency stop is.

Base, column, knee, saddle, table, head with the spindle, quill, ram and turret on some machines, handwheels, feeds and the power drawbar or drawbar. The table moves in X, the saddle in Y, and the knee or quill in Z.

Knee-and-column mills (vertical, horizontal and universal), turret mills such as the Bridgeport, bed-type mills for heavy work, planer-type mills, and CNC vertical (VMC) and horizontal (HMC) machining centers.

Place the bolt close to the work, support the heel end of the clamp on a block of the same height as the work, clamp over solid sections, keep clamps out of the cutter path, and tighten evenly. The force on the work is higher when the bolt is closer to the work.

Plain side milling cutters, staggered-tooth cutters (alternate helix for deep slots), half-side cutters (one side cutting), and interlocking cutters that adjust the slot width. Plain slab mills have teeth on the periphery only.

Approximately 0.001 to 0.004 in per tooth, increasing with cutter diameter and for softer materials such as aluminum, and reducing for small cutters and hard materials. Follow the tool maker's data.

Approximately: aluminum 300 to 800 sfpm, brass 150 to 300, mild steel 80 to 100, cast iron 60 to 80, and stainless steel 40 to 60. Carbide cutters run two to four times faster.

A dull cutter, spindle or holder runout, a feed that is too light so the cutter rubs, built-up edge, chips recut in the cut, and backlash. Use sharp cutters, a correct chip load, sufficient coolant, and clear chips from the cut.

Excess cutter overhang, loose gibs or locks, work not clamped solidly, a speed that excites vibration, and too many flutes engaged. Cures: reduce the overhang, lock unused axes, change the speed or feed, use a variable-helix cutter, and brace the work.

The cutter radius. The cutter radius must be no larger than the corner radius on the drawing. For a 0.250 in corner radius, use a cutter of 0.500 in diameter or smaller.

TiN (gold, general-purpose), TiCN (harder, steels and cast iron), TiAlN (heat-resistant, steels, stainless and high speed), and ZrN or uncoated polished cutters for aluminum, as aluminum can weld to some coatings. Diamond-like carbon coatings are used for non-ferrous work.

Soluble oil or synthetic coolant in a flood for steel, a light lubricant or mist for aluminum, and dry cutting or an air blast for cast iron. For carbide in interrupted cuts, dry cutting or a continuous flood prevents thermal shock.

Tramming sets the spindle square to the table. Mount an indicator on a tramming arm in the spindle, sweep it in X and Y across the table or a flat surface, and adjust the head until readings are equal, typically within 0.001 in over a 6 in sweep.

A standard 30 degree helix suits general work, and 45 degree or higher helix is used for aluminum and finishing. Two-flute cutters have large chip space for slotting and aluminum, and four or more flutes give a better finish and more strength in steel.

A single-point cutter held in a body that is used for light finishing cuts on flat surfaces. It runs at a lower speed than a face mill, the tool is set to the radius of the cut, and the cut is light.

The cutter bends away from the cut under load, which causes tapered walls and inaccurate sizes. Use short, large-diameter cutters, light radial cuts, sharp tools, and a spring pass to reduce its effect.

Measuring all the key features of the first part produced against the drawing before continuing with the run. Errors found are corrected in the setup, the results are recorded, and the setup is approved for production.

Milling a flat surface with a helical plain milling cutter on a horizontal arbor. The cutter is wider than the work, and helical teeth give a smooth cut. Conventional milling is used on manual machines.

About 0.0005 in or less total indicator reading for good results. Check with a dial indicator, and clean the spindle taper and collets, since dirt causes runout, uneven tooth loading and poor finishes.

Baseline (datum) dimensioning measures every feature from a common datum and keeps tolerances from adding up. Chain dimensioning measures from one feature to the next, so tolerances accumulate along the chain.

In conventional milling the cutter rotates against the direction of feed, so the chip starts thin and ends thick. In climb milling the cutter rotates with the feed, which gives a thick-to-thin chip, a better finish and a longer tool life.

A 45 degree lead angle thins the chip, spreads the load, and makes entry and exit smoother. A 90 degree lead angle makes square shoulders. Round inserts allow high feeds and are strong in tough materials.

Touch the cutter off the high spot, clear the work, set the depth for a roughing cut, mill the surface with passes that overlap, then take a light finishing cut of about 0.005 to 0.010 in. Keep the step-over below about 75% of the cutter diameter.

Clean chips and oil the ways, table screws and spindle as the chart requires, check the coolant, clean the spindle taper and collets, check the drawbar and the guards, and report any unusual noise. Avoid blowing chips into the slides with compressed air.

Spot drill, drill undersize, semi-finish bore if needed, then finish by boring or reaming. Reaming gives a tolerance of about H7 for smaller holes, and boring gives accurate position and diameter for large holes.

Check the oil and coolant, make sure the cutter, drawbar and work are tight, rotate the spindle by hand, clear tools from the table, and run the spindle at low speed for a few minutes to warm the oil.

Read the drawing and identify the datums and tolerances, choose the work holding, plan the sequence of operations, select cutters and holders, calculate speeds and feeds, and plan the measuring. Rough and finish in a logical order and keep related features in one setup.

About plus or minus 0.001 in is routine, and plus or minus 0.0005 in is possible with care and good measuring. Surface finishes of 63 to 125 microinches Ra are typical, and 32 microinches or better is possible with light finishing cuts.

R8 and ER collets, end mill holders with a Weldon flat, drill chucks, boring heads, shell mill arbors, face mill holders and hydraulic or shrink-fit holders. Collets give better accuracy and gripping than Weldon holders.

R8 (common on knee mills, retained with a drawbar), NMTB 30, 40 and 50 and the CAT, BT and ISO tapers on machining centers. NMTB and CAT use a 7:24 taper, which is self-releasing and driven by keys.

Flank wear, edge chipping, built-up edge, thermal cracking of carbide from alternate heating and cooling in interrupted cuts, and crater wear. Replace or resharpen before wear damages the finish or size.

Machine vises (plain, swivel, angle), strap clamps and T-slot bolts, parallels, V-blocks, angle plates, fixtures, a rotary table, a dividing head and magnetic chucks for small ferrous work.

Use the quill for drilling and short plunge cuts, and lock the quill for milling. For rigidity, mill with the quill retracted and raise or lower the work with the knee to set depth.

Boring bar deflection from a long overhang or heavy cuts, a dull tool, or work shifting. Use a shorter, stiffer bar, a lighter cut, and a spring pass to reduce taper.

To check that the table travel, clamps, vise and cutter clearances are correct, that the cutter rotation and feed directions are right, and that the machine will not collide with the work or fixture.

It presses the work firmly against the fixed jaw and compensates for the tilt of the movable jaw, so the work seats squarely against the fixed jaw and parallels.

A second pass at the same setting takes off the slight amount left by cutter deflection and gives a more accurate wall and a better finish.

Backlash in the table screw can let the cutter pull the table into the cut, which can break the cutter or ruin the work. Use climb milling only where backlash is eliminated, as on CNC machines, and use conventional milling on manual machines for rough cuts and scale.

Drill deep enough for the full thread depth plus allowance for the tap chamfer, usually at least three extra threads for a plug tap. Use a bottoming tap to finish near the bottom, and clear the chips.

Mark with a center punch, then spot the hole with a center drill or spot drill so the drill point is guided. Spotting stops the drill from walking, especially on rounded or slick surfaces.

Support the bar in a V-block or vise, center punch and spot drill the mark on the center line, and align the drill with that line. Clamp the bar so it cannot roll.

A 118 degree point is about 0.3 x the drill diameter in length. For a hole with a full-diameter depth of 20 mm using a 10 mm drill, set the stop to 20 + 3 = 23 mm (blind hole).

Use a slow speed, a sharp drill with a 135 to 140 degree split point, a steady, positive feed with no dwelling, plenty of cutting fluid and a rigid setup. Dwelling work hardens the surface and dulls the drill.

Use a slow speed and a tapping attachment that reverses, or turn the spindle by hand with the machine off. Use a plug tap, tapping fluid, a drill with the correct tap size, and align the tap with the hole.

Clamp a square against the drill or a ground rod in the chuck and check the table gap, or sweep a dial indicator across the table. Adjust and lock the table so it is square to the spindle.

Clamp the sheet on a wood backing, use a sharp drill ground with a small point angle or a step drill, run at low feed, and reduce pressure at breakthrough so the drill does not grab and tear the sheet.

Clamp the work in a drill press vise or to the table with T-bolts and clamps. Use V-blocks for round stock and an angle plate for vertical drilling. Never hold work by hand, since a drill can seize and spin it.

Counterboring enlarges the top of a hole with a flat bottom for a socket head screw. Countersinking cuts a cone (82 degrees for inch flat-head screws, 90 degrees for metric, 100 degrees for aircraft). Spot facing smooths a small area to give a flat seat.

Hardened bushings press-fit into a drill jig guide the drill and locate holes accurately and repeatably without layout. Liner and slip bushings allow the drill, reamer or tap to be changed in sequence.

Bench-top and floor-standing sensitive drill presses, upright drill presses, radial-arm drill presses for large work, gang drills with several spindles for sequential operations, and multi-spindle heads for drilling many holes at once.

The point, flutes, lips (cutting edges), web, margin and body, and the shank with a tang on tapered types. The usual point angle is 118 degrees, lip relief is about 8 to 12 degrees, and the chisel edge angle is about 115 to 135 degrees.

Remove the chuck key, clamp the work, secure loose clothing and tie back hair, wear safety glasses, never use gloves near the spindle, stop the machine before changing speeds or clearing chips, and use a brush or hook for chips.

Approximately: aluminum 200 to 300 sfpm, brass 150 to 300, low-carbon steel 80 to 100, cast iron 60 to 100, and stainless steel 30 to 50. Use the lower ranges for harder materials or larger drills, and follow tool maker's data.

Approximately 0.001 to 0.003 in per rev for drills under 1/8 in, 0.002 to 0.004 for 1/8 to 1/4 in, 0.004 to 0.007 for 1/4 to 1/2 in, 0.007 to 0.015 for 1/2 to 1 in, and 0.015 to 0.025 for larger drills.

Too heavy a feed, a dull or incorrectly ground drill, packed chips, work not clamped, slipping or grabbing at breakthrough, and excessive speed. Reduce feed at breakthrough to avoid grabbing.

A poorly formed chisel edge, lack of a starting mark, a long and flexible drill, too much feed, an unsupported surface, or uneven pressure. Spot with a center drill or use a short, stiff drill.

Unequal lip lengths or angles on the drill, a bent drill, a loose spindle or chuck, work shifting, and excessive feed. Check the drill with a drill gauge after sharpening.

Equal lip lengths and angles (118 degrees), correct lip relief of 8 to 12 degrees, the chisel edge centered, and the point checked with a drill gauge. Web thinning or a split point may be added on larger drills.

Cutting oil or heavy-duty soluble oil for steel and stainless, light lubricant or kerosene for aluminum, and dry or air blast for cast iron and brass. Apply fluid directly at the point and into the flutes.

Fractional sizes, number drills (#1 is 0.228 in down to #80 at 0.0135 in), letter drills (A is 0.234 in up to Z at 0.413 in), and metric sizes in millimetres. Use a drill index or chart to find the decimal size.

A self-holding taper (about 5/8 in per foot) used on drill shanks, sleeves and spindles in numbers from MT1 to MT5. Remove a tapered shank with a drift driven through the slot in the spindle, catching the drill with a cloth or wood block.

rpm = (cutting speed in sfpm x 4) / drill diameter in inches. In metric, rpm = (cutting speed in m/min x 1000) / (pi x diameter in mm). Example: a 1/2 in drill at 90 sfpm gives 90 x 4 / 0.5 = 720 rpm.

Spot, drill undersize, then bore or ream to the final size. Drilling alone is not accurate enough for close-tolerance holes, which are finished by reaming or boring.

About half the drilling speed and about two to three times the drilling feed. Leave 0.1 to 0.4 mm (0.005 to 0.015 in) for the reamer to remove, and use cutting fluid.

Keyed chucks (Jacobs type) and keyless chucks. They mount on the spindle by a Jacobs taper or a Morse taper arbor. Always remove the chuck key before starting the machine.

Chips pack in the flutes of deep holes, raise heat and torque, and can break the drill. Peck by withdrawing the drill at intervals to clear the chips and add coolant. Holes deeper than about 3 to 4 times the diameter need pecking.

It prevents the drill from damaging the table and gives support so the hole breaks out cleanly with less burr. Use parallels set apart so the drill can break through into the gap, or a scrap wood block under the work.

Burrs at the entry and exit prevent parts from seating, cause measuring errors, and can cut hands. Use a countersink or deburring tool to break the edges lightly.

Cut just outside the line, about 0.5 to 1 mm (1/32 in) of stock, and finish by filing or machining to the line. This allows for blade drift and kerf variation.

A reciprocating frame carries the blade, which cuts only on the forward stroke. The blade lifts on the return stroke, down pressure is adjustable, and a coolant pump supplies cutting fluid. The machine shuts off when the cut is complete.

Narrow blades cut tight radii, and wider blades cut straighter and resist twisting. Choose the widest blade that will still turn the smallest radius in the part.

Harder and tougher materials need slower blade speeds. As rough guidance for bimetal blades: aluminum 500 or more sfpm, low-carbon steel about 100 to 200 sfpm, and stainless steel about 50 to 100 sfpm. Always follow the blade maker's table.

Cut the blade to length with square ends, clamp the ends in the butt welder with the teeth aligned, weld them, anneal the weld to remove brittleness, and grind off the flash to the blade thickness. A poor weld is a common cause of blade breakage.

Choose the tooth pitch by wall thickness or section size so that enough teeth are in contact with the cut. Use fine pitches for thin walls and coarse pitches for solid and thick sections, and HSS or carbide-tipped blades to suit the material and production rate.

Support the stock and the cutoff piece so it cannot pinch the blade or drop, reduce the feed near the end, let the saw complete and stop, then handle the part. Hot cut parts should cool before measuring.

Make sure the blade is running at full speed and not touching the work, lower it gently with light pressure, and start on a flat face rather than a sharp edge or corner. On tubing and angle iron, orient the work so the cut begins on the flat of the section.

Check the wheel for cracks and ring-test it, confirm the wheel's rated rpm is at or above the spindle speed, use blotters and matched flanges, tighten only snugly, fit the guard, and stand clear while it runs at full speed for about one minute before cutting.

At least 3 teeth should be in contact with the work, so use finer pitches for thin sections and tubing, and coarser pitches for thick or solid sections. Variable-pitch blades reduce vibration when cutting changing sections.

Teeth must point in the direction of blade travel at the cutting zone, which is down toward the table on a vertical band saw. If the teeth face backward, turn the blade inside out or flip it before installing.

Adjust the feed control (often a hydraulic valve) so the blade cuts steadily and produces well-curled chips. The feed should be heavy enough to cut rather than rub and light enough that the blade does not deflect.

Loosen the table lock, tilt the table to the required angle using its scale, check the angle with a protractor or bevel gauge against the blade, lock the table, and make a trial cut on scrap.

Clamp the work firmly in the vise with a support on long stock, check squareness with a square from the blade to the vise face, set the angle on the mitre scale, and set the length stop for repeat cuts. Allow for the kerf and for extra stock for finishing.

Run it at reduced feed pressure for the first few cuts, about half normal, until the tooth tips take a slight edge wear. This avoids chipping the sharp teeth and gives longer blade life.

Carbon steel (low cost, softer metals and general use), bimetal (HSS tooth edge welded to a flexible alloy back, the most common for metal), and carbide-tipped (hard alloys and abrasive materials, high production).

Excess blade tension, a cracked or poor weld, guides too tight or worn, a blade speed that is too fast or too slow for the material, forcing the cut, or a blade twisted by a heavy side load.

Set the guide arm as close to the work as possible, adjust the guides to just touch the blade with the clearance specified by the manufacturer, and set the back-up bearing just behind the blade. Poor guide settings make the blade wander.

Keep fingers out of line with the blade, set the guide close to the work, use push sticks for small parts, never remove chips by hand while the saw runs, wear eye protection, and never reach around a moving blade.

Lock out the saw, release the tension, open the wheel guards, fit the blade over the wheels with the teeth pointing in the direction of travel, seat it between the guides and back-up bearings, tension it, track it by hand, close the guards, and then run the saw briefly to check the tracking.

A dull blade, loose or worn guides, low tension, excessive feed pressure, the wrong pitch for the section, or poor workholding. Check the guides, tension and feed first.

A pitch that is too coarse for the section, an excessive feed, starting a cut on a sharp corner, or hard spots in the material. Fine pitches in thin-wall tubing are a common remedy.

Fine powder or dust means the feed is too light or the blade is dull. Blue or burnt chips mean the speed or feed is too high or coolant is lacking. Thick, heavy slugs mean the feed is too heavy. Well-curled silver chips mean correct conditions.

Too light, the teeth rub and glaze, work harden the cut surface and dull quickly. Too heavy, the blade deflects, makes crooked cuts, strips teeth or breaks.

A cold saw uses a slow-turning circular HSS or carbide-tipped blade that carries heat away in the chips and leaves a clean, burr-free cut. An abrasive cutoff saw uses a bonded abrasive wheel at high speed, cuts hard materials quickly, but produces heat, sparks, burrs and requires a wheel guard.

Blade speed (sfpm) = pi x wheel diameter (in) x rpm / 12. Example: a 12 in wheel turning 400 rpm gives 3.1416 x 12 x 400 / 12 = about 1257 sfpm.

Set is the bending of teeth to the side to make a kerf wider than the blade body so the blade does not bind. Raker set (a left, right and straight pattern) is the general standard, wave set suits thin sections and tubing, and straight set is used for some soft materials.

Guards in place, the blade condition and tension, guide settings, coolant level and flow, chip brush or conveyor, emergency stop, work clamped securely, and the area clear of loose items.

Tension the blade according to the saw maker's gauge or setting, then adjust the wheel tilt so the blade tracks centered on the wheels with the gullets just clear of the wheel edge. Too little tension causes wandering cuts and too much shortens blade life.

It cools the blade and work, lubricates the cut, flushes chips from the gullets and extends blade life. Flood or mist is applied directly to the cutting zone. Some materials such as cast iron are often cut dry.

Coarse grits (10 to 24) remove stock quickly, medium grits (30 to 60) are general-purpose, fine grits (70 to 180) give good finishes, and very fine grits (220 to 600) give the finest finishes. Finer grits cut slower.

A typical graduation is 0.0001 in (or 0.002 mm), so one division moves the wheelhead 0.0001 in. Always approach the final reading from the same direction to remove backlash.

Use light magnetic chuck force with shims, take light cuts with a sharp wheel and plenty of coolant, flip the part often so that both sides are ground alternately, and use stress-relieved material.

The work is supported on a work-rest blade between the grinding wheel and a slower regulating wheel, which controls the work speed. The through-feed rate is set by tilting the regulating wheel: F = pi x D x N x sin(angle), where D and N are the regulating wheel diameter and speed.

It uses magnetic force to hold ferrous work flat on the table. Clean the chuck face, put the work on it fully, and switch it on. Small parts need blocking around them, and non-magnetic work needs a vise or fixture.

A small wheel, usually about two thirds of the bore diameter, runs at a very high spindle speed on a quill to keep the surface speed up. The quill must be as short and stiff as possible, and coolant must flush the swarf out of the bore.

A slow traverse gives a fine, smooth wheel and fine finishes. A fast traverse leaves a coarse, open wheel that cuts faster but leaves a rougher finish.

Grind one face flat, turn it over and grind the opposite face parallel, then hold the block against an angle plate or a square block to grind the adjacent edges square. Check squareness with a precision square.

Mount the work between centers in the workhead and tailstock with a dog, set the table swivel for a straight cut or a taper, set the work speed (far slower than the wheel), set the table traverse stops, and take infeed with the wheelhead. Dress the wheel before use.

Hold the diamond in a holder on the chuck, angled about 3 to 15 degrees in the direction of wheel rotation, and traverse it across the wheel with coolant, taking cuts of 0.0005 to 0.001 in. Do not let the diamond overheat, and do not dress dry.

A is the abrasive (aluminum oxide), 60 is the grit size, K is the grade (hardness), 5 is the structure (spacing of grains) and V is the bond (vitrified). Other bonds are B (resinoid), R (rubber), E (shellac) and M (metal).

Inspect it and ring-test it, check the rated rpm against the spindle speed, fit it freely on the spindle (not forced), use blotters and matching flanges of at least one third of the wheel diameter, tighten the nut firmly, fit the guard, and run it for one minute while standing clear.

Remove burrs and rust with a fine stone, wipe it clean, and remove chips. Chuck faces are lightly ground in place to make them flat and parallel with the table travel.

With silicon carbide (green) or diamond wheels, using coolant and light cuts. Carbide is brittle and heat-sensitive, so avoid shock and heat.

Use a friable aluminum oxide wheel (white or pink) of soft to medium grade, light cuts and ample coolant. High-speed steel and highly alloyed steels are better ground with CBN wheels.

Grind one face flat, then turn the part over and grind the opposite face to the thickness. Deburr between operations and check the thickness with a micrometer at several points.

Hard materials need softer wheels so that dull grains break out and expose new grains. Soft materials need harder wheels. Grade letters run from A (soft) to Z (hard).

Lower the wheel slowly until the first sparks appear or a paper feeler just drags, then set the downfeed dial to zero. Move off the work, and then bring the wheel down by the amount of the first cut.

Aluminum oxide for steels, silicon carbide for cast iron, non-ferrous metals and carbide, cubic boron nitride (CBN) for hard steels and HSS, and diamond for carbide, ceramics and glass.

Fine thermal cracks that are at right angles to the grinding direction, caused by localized heat. Prevent them with a soft wheel, light cuts, ample coolant and stress relief. Find them by magnetic particle inspection.

Fine metal dust is a fire and explosion risk (magnesium in particular), and abrasive and metal dusts are harmful to breathe. Use dust collection, coolant or wet grinding, and respirators where needed. Do not mix dry and wet grinding.

Base, column, wheelhead, saddle, table, magnetic chuck, wheel guard and the controls: the table (longitudinal) traverse, the cross feed and the vertical downfeed handwheels with dials.

Surface grinders (horizontal or vertical spindle, reciprocating or rotary table), cylindrical grinders (between centers), centerless grinders, internal grinders, tool and cutter grinders and jig grinders.

Check the wheel and ring-test it, use the guard, stand to the side when starting, wear a face shield and safety glasses, never exceed the rated rpm, grind only on the face of straight wheels, and do not apply heavy side pressure.

An unbalanced wheel, loose spindle bearings, a glazed or hard wheel, vibration from nearby machinery, or a loose setup. Cure it by balancing and dressing the wheel, lightening the cut and checking the machine.

Heat from a dull or glazed wheel, too heavy a cut, too little coolant, or a wheel that is too hard. The surface discolors and can be tempered or rehardened. Nital etching shows dark and light patches where the surface is burned.

Roughing uses a downfeed of about 0.001 to 0.002 in per pass, and finishing uses about 0.0002 to 0.0005 in. Cross feed is about 1/4 to 1/2 of the wheel width for roughing and 1/8 to 1/4 for finishing.

Typically 8 to 32 microinches Ra (0.2 to 0.8 micrometres), with finer finishes possible with fine wheels, light cuts and spark-out. Lapping or honing can go finer.

Sharpening and reconditioning end mills, reamers, milling cutters and other tools. It uses cup and dish wheels, a tooth rest and an adjustable head to give the correct clearance angles.

Letting the wheel traverse across the work several times without further downfeed until sparks stop. It removes the spring in the machine, the wheel and the work, and gives the final size and flat surface.

Truing makes the wheel round and true to the spindle and restores its shape. Dressing removes loaded or dull grains and exposes fresh, sharp grains. A diamond dresser usually performs both.

It is marked on the blotter or wheel in rpm and must never be exceeded. Vitrified wheels typically run at about 6000 sfpm (30 m/s), and resinoid wheels can run faster, up to about 9500 sfpm.

Suspend the vitrified wheel freely, tap it lightly with a non-metallic tool at 45 degrees on each side, and listen. A clear ring means the wheel is sound, and a dull thud means the wheel may be cracked and must not be used.

Loading is metal packing into the pores of the wheel, caused by soft or gummy metals, a hard wheel or too little coolant. Glazing is dull grains that do not break out, caused by too hard a wheel or too fine a grit. Both are cured by dressing and, if needed, a softer or coarser wheel.

Clean the table and chuck, remove burrs from the work, put the work on the chuck and turn it on, set the table reversing dogs, set the cross feed travel, lower the wheel carefully to the work, and touch off the wheel with light sparks to set zero.

Surface and cylindrical grinding commonly hold plus or minus 0.0001 in (0.0025 mm), and plus or minus 0.00005 in is possible with a stable temperature and careful measurement.

When it loads with metal, glazes, loses its shape or cuts poorly, when the finish becomes poor, or when a different finish is needed. Dress before the finishing passes.

An unbalanced wheel vibrates, which gives chatter marks, poor finish and shorter bearing life. Wheels are balanced on a balancing stand with an arbor, using adjustable weights in the flange.

It carries heat away from the cut, flushes the swarf, prevents loading of the wheel, improves the surface finish and protects the work from thermal damage. Coolant must be clean and directed at the cut.

Residual magnetism holds chips and swarf on the part, affects measurement, and can disturb nearby instruments and tools. Pass the part over a demagnetizer or use the chuck's demagnetizing cycle.

SAE Grade 5 bolts have 3 radial lines on the head and Grade 8 has 6 lines. Metric classes include 8.8, 10.9 and 12.9. Tighten with a torque wrench to the specified value, in stages, in a crisscross pattern.

Coat the surface with layout dye (blue) for contrast, scribe lines with a hardened scriber, and mark intersections with a prick punch (about 30 degrees). A center punch (about 90 degrees) enlarges the mark so a drill starts accurately.

Degrease with an approved solvent or hot wash. Dye penetrant inspection finds surface cracks in non-porous materials, and magnetic particle inspection finds surface and near-surface cracks in ferromagnetic materials.

Use the correct snap-ring pliers for external or internal rings, avoid over-spreading, make sure the ring sits fully in its groove, and replace rings that are bent or sprung.

Drill out the damaged threads using the specified drill, tap the hole with the special insert tap, install the coiled insert with the installation tool, and break off the tang. The insert restores the thread size and strengthens soft materials such as aluminum.

Apply penetrating oil, lock two nuts together on the stud and turn the lower nut, or use a stud extractor. If the stud is broken off, use a screw extractor. Protect the threads in the hole from damage.

Use a puller or press and apply force to the ring that has the tight fit, the inner ring when pressed on a shaft. Never drive force through the balls or rollers. Take note of the bearing orientation and shield or seal sides.

About 14 TPI for soft metals and thick sections, 18 TPI for mild steel and general work, 24 TPI for angle iron and thicker tubing, and 32 TPI for thin tubing and sheet. At least 3 teeth should be in contact with the work at all times.

The lip faces the fluid being sealed. Lubricate the lip, protect it from keyways and sharp edges with a sleeve or tape, and press the seal in squarely using a driver on the outer rim.

Press out the old bushing, clean the bore, press in the new bushing squarely with a driver and a little lubricant, check oil hole alignment, and ream or bore to the final size after installation if specified.

Support the work on a solid base or blocks, align the part with the arbor, use an arbor or driver of the correct size, lubricate the fit, and apply steady pressure. Keep hands clear and stay within the press capacity.

Chamfer the end of the rod, hold the adjustable round split die in a die stock with the tapered lead side against the work, keep it square, and turn forward and back to break the chips. Use cutting fluid and adjust the die to the thread fit.

Tap drill = major diameter - pitch. Example for M8 x 1.25: 8 - 1.25 = 6.75 mm. In practice the standard 6.8 mm drill is used.

Tap drill = major diameter - (1 / threads per inch). This gives about a 75% thread. Example for 1/4-20: 0.250 - 0.050 = 0.200 in, so use a #7 drill (0.201 in).

Always fit a handle, cut on the forward stroke, lift on the return, and keep even pressure. Clean with a file card to remove pinning, because chips caught in the teeth scratch the work. Chalk reduces pinning, and draw filing with a smooth file gives a fine finish.

They locate parts accurately and repeatably. Hardened ground dowels are slightly oversize and pressed into reamed holes. Two dowels spaced far apart locate the parts. Blind holes need an air vent so the pin can seat.

A 118 degree point is the general-purpose standard for mild steel and many materials. A flatter 135 to 140 degree point, often with a split point, is used for harder materials and stainless steel because it reduces walking and thrust.

Keep the tool rest within 1/8 in (3 mm) of the wheel and the tongue guard within 1/4 in (6 mm). Ring-test new wheels, wear a face shield, stand to the side at start-up, grind only on the wheel face, and dress the wheel when it loads or glazes.

Grade AA is for the laboratory, Grade A is for the inspection room, and Grade B is for the tool room or shop floor. The flatness tolerance is tightest for AA and loosest for B.

Unified and ISO metric threads have a 60 degree thread angle. Acme threads are 29 degrees, metric trapezoidal threads are 30 degrees, and NPT pipe threads are 60 degrees with a taper of 3/4 in per foot (1:16).

Taper tap: 8 to 10 threads of chamfer, used to start threads. Plug tap: 3 to 5 threads of chamfer, the general-purpose tap. Bottoming tap: 1 to 2 threads of chamfer, used to cut threads close to the bottom of a blind hole after the plug tap.

Single cut files have one set of parallel teeth and give a smooth finish. Double cut files have crossed teeth and remove stock faster. Coarseness increases from dead smooth, smooth and second cut, to bastard and coarse.

V-blocks hold round work for layout and inspection. Angle plates hold work square to the surface plate or machine table. Parallels are matched, ground bars that support work evenly in a vise or on a table.

H = L x sin(angle) = 5 x sin 30 = 5 x 0.5 = 2.500 in. Build the stack with gauge blocks that add up to 2.500 in.

A ball-peen hammer strikes punches and chisels and sets rivets. A soft-faced hammer (copper, brass, plastic, rawhide) is used on finished surfaces. A dead-blow hammer reduces rebound. Check that the head is tight on the handle before use.

A vernier, dial or digital height gauge with a scriber or probe measures and scribes heights from the surface plate. It is zeroed on the plate. A simple surface gauge with a scriber is used for rough layout.

The outer part is heated, or the inner part is chilled with dry ice or liquid nitrogen, so the parts slide together, then size equalizes and the fit grips. Bearings are heated in an oil bath or induction heater to no more than about 120 degrees C (250 degrees F), never with a torch.

Scraping removes tiny amounts of metal to produce flat bearing surfaces and to fit machine ways. Marking compound (Prussian blue) on a master surface transfers to the high spots, which are scraped away, and the process repeats. Scraping also leaves small pockets that hold oil.

A finishing process in which loose abrasive in a carrier fluid is rubbed between the work and a softer lap (cast iron or copper). It removes very small amounts of material and gives very flat surfaces and fine finishes. Common abrasives are silicon carbide, aluminum oxide and diamond.

Teeth point away from the handle so the saw cuts on the push stroke. Apply light pressure on the forward stroke and lift slightly on the return, use the full blade length, and cut at about 40 to 50 strokes per minute. Keep the blade tight in the frame.

Keep the tap square to the work, turn forward about a half turn and then back about a quarter turn to break the chip, and use tapping fluid. A spiral-point (gun) tap pushes chips ahead in through holes, and a spiral-flute tap pulls chips out of blind holes.

Remove only a small amount of stock, about 0.1 to 0.2 mm (0.004 to 0.008 in), use cutting fluid, keep the reamer square, and turn it clockwise only, including when withdrawing it. Turning it backward dulls the cutting edges.

sin(angle) = H / L, where H is the height of the gauge block stack and L is the distance between the roll centers (commonly 5 in, 10 in, 100 mm or 200 mm). It is most accurate for angles below about 45 degrees.

The standard taper is 1/4 in per foot (1:48) on the diameter. Drill the holes, then ream with a taper pin reamer until the pin fits snugly with the small end just flush or slightly proud.

Check for pitting, scoring, uneven wear patterns, cracked or broken teeth, tooth thickness and backlash. A worn gear set is usually replaced as a matched pair.

Clean and inspect it, measure wear against the drawing or manufacturer's specifications, decide whether to repair or replace, record findings, replace wear items such as bearings and seals, reassemble with the correct fits and torque, and test run.

Parallel keys (square or rectangular), Woodruff keys (half-moon), and gib-head taper keys. A square key width is roughly one quarter of the shaft diameter. A keyseat is cut in the shaft and a keyway in the hub.

Soft jaw liners made of aluminum, copper, brass or fibre protect finished surfaces from marking. Do not hammer on the movable jaw, and support thin parts on parallels so they do not distort.

The mushroomed edge can crack and throw sharp chips. Grind off the mushroom to restore a chamfered head, and wear safety glasses when chiseling or punching.

Burrs cut hands, spoil fits and cause false measurements. Remove them with files, scrapers, a swivel-blade deburring tool, abrasive stones or pads, or a chamfer tool, and then re-check dimensions.

Upper limit 25.02 mm, lower limit 24.96 mm. The total tolerance is 25.02 - 24.96 = 0.06 mm.

Tensile strength is the maximum stress before breaking. Yield strength is the stress at which permanent deformation starts. Ductility is the ability to stretch, malleability to be hammered or rolled, hardness resistance to indentation, toughness resistance to fracture, and brittleness a tendency to break without deforming.

Low carbon (up to about 0.30%) is soft and easy to machine and weld but not hardenable by quenching. Medium carbon (0.30 to 0.60%) is hardenable and tougher. High carbon (0.60 to about 1.0% and over) hardens to a high level but is brittle.

Pick blocks from the largest to the smallest without repeating, and eliminate the last digits first. For example, 1.4375 = 1.0000 + 0.2000 + 0.1370 + 0.1005. The blocks are wrung together and cleaned and stored with oil afterward.

M10 x 1.5 is a metric thread with a 10 mm major diameter and a 1.5 mm pitch. 1/2-13 UNC-2B is a unified coarse thread with a 1/2 inch major diameter, 13 threads per inch and a class 2 fit; B means internal thread (A means external).

A spark test on a grinder: low-carbon steel gives long, straw-coloured streaks with few bursts, and high-carbon steel gives many branching bursts. Magnet and file tests, colour codes and mill markings help. Certified material is traced by heat number.

Rockwell measures depth of an indentation: the C scale uses a diamond cone and 150 kgf for hard steels, and the B scale uses a 1/16 in ball and 100 kgf for softer metals. Brinell uses a 10 mm ball (3000 kgf for steel). Vickers uses a diamond pyramid and works for all hardness.

Multiply by 25.4, because 1 inch is exactly 25.4 mm. For example, 2.5 in = 63.5 mm. To convert millimetres to inches, divide by 25.4.

The first two digits show the alloy type and the last two show carbon in hundredths of a percent. For example, 1018 is plain carbon steel with about 0.18% carbon, and 4140 is chromium-molybdenum steel with about 0.40% carbon.

0.375 + 0.012 = 0.387 in. Each sleeve line is 0.025 in and each of the 25 thimble divisions is 0.001 in. Add any extra sleeve lines past the 0.375 mark.

Dress the wheel, set the tool rest close to the wheel (about 1.5 mm or 1/16 in), grind the clearance and rake angles with light pressure, keep the tool moving, and cool it in water often to avoid burning. Wear safety glasses and a face shield.

12.00 + 0.50 + 0.37 = 12.87 mm. Each thimble division is 0.01 mm, and two turns of the thimble equal 1 mm.

Free-cutting brass (such as C360) machines easily at high speeds. Use zero or slightly negative rake tools so the tool does not dig in or grab, and keep the setup rigid. Chips are small and easy to clear.

Wipe them clean after use, apply a light film of oil to bare steel, keep them in cases, never drop or overtighten them, check the zero before use, and keep them away from chips, coolant and magnets.

They harden only the surface while the core stays tough. Carburizing adds carbon to low-carbon steel before quenching, nitriding diffuses nitrogen at a lower temperature without quenching, and induction or flame hardening heat the surface quickly and quench it.

Explain the purpose and safety points, demonstrate the task, let the apprentice do it while you watch, give clear and respectful feedback, and encourage questions. Record the apprentice's progress in the logbook for hours and skills.

Annealing softens steel by slow cooling. Normalizing refines grain by air cooling. Hardening heats above the critical temperature and quenches. Tempering reheats a hardened part below the critical temperature to reduce brittleness and set the final hardness.

Form (flatness, straightness, circularity, cylindricity), profile (line and surface), orientation (perpendicularity, parallelism, angularity), location (position, concentricity, symmetry) and runout (circular and total). Form tolerances need no datum.

6061 (magnesium and silicon) is a general-purpose, weldable alloy usually supplied as T6. 7075 (zinc) is very high strength. 2024 (copper) is strong for aircraft parts. 5052 (magnesium) is formable and corrosion-resistant. 1100 is nearly pure and soft.

Object (visible) lines are thick and continuous, hidden lines are short dashes, center lines are long-short-long, dimension and extension lines are thin and continuous, cutting-plane lines are thick with long-short-short dashes, and phantom lines show alternate positions.

Class A: ordinary combustibles. Class B: flammable liquids and gases. Class C: energized electrical equipment. Class D: combustible metals such as magnesium, titanium and zirconium chips. Class K: cooking oils and fats. Never use water on a magnesium chip fire.

Use sharp tools with positive rake, high speeds, light cuts and good chip clearance. Plastics are heat-sensitive and soft, so use air or mist cooling and avoid heat build-up. Support thin work well because parts can flex and relax later.

They work-harden and conduct heat poorly, so use slow cutting speeds, rigid setups, sharp positive tools, steady feeds that never dwell, and plenty of coolant. Heat stays at the cutting edge, so tool wear is rapid.

Gray iron has graphite flakes, is easy to machine, machines dry and produces powdery chips. Ductile (nodular) iron has graphite spheres and is stronger and more ductile. White iron is very hard and brittle. Malleable iron is heat-treated white iron.

Plunger-type indicators measure along the plunger axis, and lever (test) indicators measure at an angle. Keep the lever contact at about 90 degrees to the surface to avoid cosine error, preload the indicator, and use a rigid stand. Total indicator reading (TIR) is the full needle swing.

A rectangle read from left to right: the geometric characteristic symbol, the tolerance value (with a diameter symbol if the zone is cylindrical, and any material condition modifier), and then the datum references in order of precedence.

Plan the lift, know the weight, use cranes, hoists or lifting aids, check slings and lifting points before use, keep the load low, stay clear of the load, and use hand signals. Lift with your legs and ask for help for heavy loads.

Notify affected workers, shut down the machine normally, isolate every energy source, apply your own lock and tag, release or block stored energy, and verify zero energy by trying to start the machine. The person who applies a lock is the only one who removes it.

Clearance fit (the shaft is always smaller than the hole), interference fit (the shaft is always larger than the hole, so the parts are pressed together) and transition fit (the result may be either clearance or interference).

Supplier and workplace labels, safety data sheets (SDS), and worker education and training. Hazards are shown with standard pictograms, signal words (Danger or Warning) and hazard statements.

Straight oils, soluble (emulsion) oils, semi-synthetic and synthetic fluids. They cool the tool and work, lubricate to reduce friction, flush chips away and protect against rust. Concentration is checked with a refractometer.

Sixteen sections covering identification, hazards, composition, first aid, firefighting, spill response, handling and storage, exposure controls and PPE, physical properties, stability, toxicology, disposal and transport information. Machinists use it for cutting fluids, solvents and cleaners.

Comparing the instrument with a reference standard that is traceable to a national standard such as the National Research Council of Canada, at regular intervals. Record the date and result, label the tool, and remove it from use if it is out of calibration.

Roughness average, the arithmetic mean height of the surface irregularities, measured in micrometres (microinches). As a general guide, milling gives about 1.6 to 3.2 micrometres Ra, finish turning 0.8 to 1.6, and grinding 0.2 to 0.8 or finer.

Daily lubrication of ways and spindle per the manual, checking oil and coolant levels, cleaning chips, inspecting guards and safety devices, checking gibs and backlash, and keeping a maintenance log. Report abnormal noise, vibration or leaks.

Rough before finishing, machine a datum face or bore first, do operations that need accurate relationship to each other in one setup, drill before reaming or boring, and do heat treatment between roughing and finishing when distortion is likely.

Job status, setups and offsets in use, tool wear and tool changes, quality problems, inspection results, equipment faults, safety concerns and material shortages. Clear written notes avoid scrap and repeated errors.

A view that shows the inside of a part as if it were cut along a cutting-plane line. The surfaces that were cut are shown with thin hatching lines, usually at 45 degrees. Types include full, half, offset and revolved sections.

Lubrication of the ways, wear and scoring, gib adjustment to remove play without binding, and backlash in the lead screws. Loose gibs cause chatter and poor finish. Over-tight gibs cause stiff movement and wear.

The measuring instrument should be at least ten times more precise than the tolerance being checked. Measure at standard temperature of 20 degrees C (68 degrees F), since steel parts and instruments change size with temperature.

Bilateral tolerance varies both ways from the nominal, such as 25.00 plus or minus 0.05. Unilateral tolerance varies in only one direction, such as 25.00 +0.00/-0.05. Limit dimensioning gives the maximum and minimum sizes directly, such as 25.05 / 24.95.

From most to least effective: eliminate the hazard, substitute something safer, use engineering controls (guards, ventilation), use administrative controls (procedures, training, signs), and use personal protective equipment as the last line of defence.

The smallest value it can read. Common values are 0.001 in (inch vernier), 0.02 mm (metric vernier), and 0.0005 in or 0.01 mm for digital calipers. Calipers are used for measurements to about 0.02 mm.

Additions such as sulfur or lead (for example 12L14 or 1215) help the chip break and reduce friction, which gives better surface finish and tool life. Gummy steels like 1018 form long stringy chips.

CSA-approved safety glasses with side shields, CSA-approved safety footwear (green triangle puncture-resistant sole, steel or composite toe), hearing protection when noise reaches 85 dBA or more, and close-fitting clothing. No gloves, loose sleeves, rings, watches or dangling jewelry near rotating machinery, and long hair must be tied back.

Third-angle projection. The top view is placed above the front view and the right-side view is placed to the right of the front view. European drawings often use first-angle projection, so the symbol on the drawing should be checked.

Material grade and certification against the work order, saw kerf, extra stock for facing and finishing (commonly 1 to 3 mm), and the effect of bar straightness. Keep heat numbers with the material when traceability is required.

When a drawing is unclear, dimensions conflict or tolerances cannot be achieved, when material or tooling does not match the job, or when the setup or process is unsafe. Ask before cutting, since errors in metal cannot be undone.

303 has added sulfur (or selenium) that helps chips break. 304 work-hardens quickly and makes tough, stringy chips, so it needs sharp tools, rigid setups, positive feeds and no dwelling.

They keep hands, hair and clothing away from rotating parts, and flying chips and coolant away from the operator. Removing a guard exposes the worker to entanglement and ejection hazards. A damaged guard is reported and the machine is taken out of service.