NIMS CNC cheat sheet

Lockout/tagout requires isolating every energy source, dissipating stored hydraulic, pneumatic, gravity, and capacitor energy, and verifying zero energy before entering an enclosure.

ANSI Z87.1 safety glasses are the minimum primary eye protection at any machine; a face shield is secondary protection and is not worn alone.

OSHA limits compressed air used for cleaning to 30 psi at the nozzle when chips could be blown onto skin.

Hearing protection is required at 85 dBA as an 8-hour time-weighted average; every 3 dB increase halves the allowable exposure time.

The OSHA permissible exposure limit for mineral oil mist is 5 mg/m3; NIOSH recommends 0.4 mg/m3 thoracic particulate over a 15-minute sample.

Magnesium and titanium fines are Class D fire hazards; water and CO2 react or spread the fire, so dry powder or graphite agents are used.

Metalworking fluid concentration is checked with a refractometer; tramp oil and low concentration drive dermatitis and microbial growth.

An interlocked enclosure door must prevent spindle rotation when open; E-stops are latching with manual reset and never replace lockout/tagout.

In third-angle projection (US practice) the top view is drawn above the front view and the right-side view to the right of the front view; first-angle reverses these positions.

Form tolerances (flatness, straightness, circularity, cylindricity) reference no datum; orientation tolerances reference one datum; location tolerances reference the full datum frame.

MMC is the smallest hole or largest shaft; bonus tolerance equals the amount the actual feature size departs from MMC toward LMC.

A datum reference frame removes six degrees of freedom: primary datum three, secondary two, tertiary one.

Rule #1 (envelope principle): at MMC a size feature may not violate its perfect-form boundary, so the size tolerance also limits form error unless the drawing overrides it.

For a +/-0.005 in coordinate tolerance on both axes, the equivalent diametral position tolerance is 2 x sqrt(0.005^2 + 0.005^2), about 0.014 in.

Ra is the arithmetic average roughness and Rz the average peak-to-valley of five sampling lengths; the default cutoff is 0.8 mm (0.030 in).

The title block tolerance block supplies default tolerances for untoleranced dimensions by decimal place, plus material, scale, units, and revision level.

A 0-1 in micrometer advances 0.025 in per revolution with a 25-division thimble, giving 0.001 in; a vernier sleeve resolves 0.0001 in.

Standard reference temperature is 68 F (20 C); steel expands about 6.5 micro-inch per inch per F and aluminum about 13.

Sine bar: sin(theta) = gage stack height / roll center distance; a 5 in sine bar needs a 0.5000 in stack for 5.739 degrees.

Gage R&R percent study variation below 10% is acceptable, 10-30% is marginal, and above 30% is unacceptable.

Three-wire thread measurement: over-wire dimension M = E + 3W - 0.86603P for 60-degree threads, where E is pitch diameter, W wire size, P pitch.

Go/no-go plug gages: the go member must enter the full length by hand; the no-go member should not enter more than two turns.

CMM probe qualification establishes effective stylus ball diameter; temperature variation and probe force are the dominant measurement error sources.

Height gages and indicators are referenced to the surface plate, so plate flatness and cleanliness directly affect the reading.

RPM = (3.82 x SFM) / D with D in inches; equivalently SFM = pi x D x RPM / 12.

Feed rate in IPM = RPM x number of teeth x chip load per tooth.

Carbide runs roughly 2-4 times the surface speed of HSS in the same steel; TiAlN and AlTiN coatings raise hot hardness and permit dry or near-dry cutting.

Positive rake lowers cutting force and power on aluminum and low-carbon steel; negative rake gives a stronger edge for interrupted cuts and cast iron.

Built-up edge forms at low speed and high feed, then breaks away and ruins finish; raising speed and applying coolant eliminates it.

300-series stainless and nickel alloys work-harden; maintain constant feed, never rub or dwell, and keep depth of cut below the hardened skin.

Magnesium is machined dry or with a special mineral-oil coolant; water-based coolant generates hydrogen and creates a fire hazard.

Taylor tool life V x T^n = C: for carbide with n near 0.25, doubling cutting speed reduces tool life by roughly 6-8 times.

G00 rapid, G01 linear feed, G02 clockwise arc, G03 counterclockwise arc; arcs use I, J, K center offsets from the start point or an R radius word.

G20/G21 select inch/metric, G90/G91 select absolute/incremental, G94 sets feed per minute and G95 feed per revolution.

G43 applies tool length compensation from the H register; G41 and G42 enable cutter compensation left and right using the D register.

M03/M04 start the spindle CW/CCW, M05 stops it, M06 changes tools, M08/M09 switch coolant on/off, M30 ends the program and rewinds.

G81 drill, G82 drill with dwell, G83 peck drill with Q peck depth, G84 tap, G76 fine bore; G80 cancels all canned cycles.

G54-G59 are work coordinate systems; G53 commands machine coordinates and ignores the active work offset.

Cutter compensation must be applied on a linear lead-in move at least as long as the tool radius to avoid gouging the part.

A CAM post processor converts toolpath (cutter location) data into machine-specific G-code; arc format, tool change, and cycle syntax must be verified per control.

A tool length offset is the distance from the machine gage line or reference surface to the tool tip, stored in the H register and applied by G43.

Work offsets G54-G59 set part zero; X and Y are located with an edge finder (add half its diameter) or a spindle probe.

The 3-2-1 principle locates a part with three points on the primary plane, two on the secondary, and one on the tertiary, removing all six degrees of freedom.

Vise jaws must be indicated parallel to the X axis to about 0.0005 in over the jaw length before machining.

Soft jaws are bored in place while clamped at the diameter being held so the bored profile matches the part under clamping pressure.

Tool runout checked at the flutes should stay near or below 0.0005 in TIR; greater runout shortens tool life and cuts oversize slots.

Climb (down) milling gives better finish and longer tool life on a backlash-free ball screw machine; conventional milling is used where backlash is significant.

Taper and collet bores are cleaned and blued before loading; chips or dried coolant in the taper cause runout and poor surface finish.

Feed override typically ranges 0-200% and rapid override 25/50/100%; single block executes one block at a time and M01 stops only when optional stop is enabled.

Dry run increases traverse rates for path checking; it is used with the tool clear of the part or with the spindle stopped.

Cpk = min(USL - mean, mean - LSL) / (3 sigma); 1.33 is the usual minimum acceptable value for a controlled process.

OEE = availability x performance x quality, where world-class performance is about 85%.

First article inspection verifies the first conforming part against every drawing characteristic before the production run is released.

Spindle load meters read percent of rated power; sustained cuts above about 80% accelerate spindle bearing wear.

Tool life management counts cutting time or parts per tool and forces a change at a preset limit.

Coolant concentration measured by refractometer typically runs 6-10% for general machining; low concentration causes rust, odors, and rapid tool wear.

Backlash and lost motion are checked by indicating a part and reversing the axis; a healthy ball screw axis shows less than about 0.0005 in.

A way lube alarm indicates an empty reservoir, a broken line, or a failed metering unit, not simply low oil.

Root-cause tools: 5 Whys for a single event, fishbone (Ishikawa) for cause categories, and Pareto ranking to attack the few causes producing most defects.

Chatter is corrected by reducing tool overhang first, then adjusting speed to a stable lobe and checking fixture and toolholder rigidity.

Drawbar force below roughly 2000 lb on a CAT40 spindle allows tool slip and poor finish; Belleville washers and retention knobs are the usual causes.

Coolant pH should stay near 8.5-9.5; a falling pH signals bacterial growth, odor, and corrosion risk.

Preventive maintenance is scheduled by run hours or cycles: way lube filters, coolant changes, belt tension, and spindle taper cleaning.

Thermal growth drifts a machine during warm-up; run the spindle warm-up program and recheck work and tool offsets before close-tolerance production.