NIMS CNC flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Lockout/Tagout

A procedure that isolates every energy source, releases stored hydraulic, pneumatic, and spring energy, and verifies zero energy before anyone enters the machine enclosure.

Class D extinguisher

The extinguisher class for combustible metals such as magnesium and titanium; water and CO2 are dangerous on these fires because they react with or spread the burning chips.

Oil mist exposure limit

OSHA's permissible exposure limit for mineral oil mist is 5 mg/m3 as an 8-hour average; NIOSH recommends a much lower 0.4 mg/m3 thoracic limit.

Tramp oil

Hydraulic and way-lube oil that leaks into the coolant sump; it feeds bacteria, causes smoke and dermatitis, and is removed with a skimmer or coalescer.

Third-angle projection

A drawing layout used in US practice where the top view is placed above the front view and the right-side view is placed to the right of the front view.

Maximum material condition

The size at which a feature contains the most material: the smallest hole or largest shaft. Position tolerance at MMC gains bonus tolerance as actual size departs from MMC.

Datum reference frame

Three mutually perpendicular planes established by the primary, secondary, and tertiary datums; they remove three, two, and one degrees of freedom respectively.

Rule 1 envelope principle

A size tolerance limits form error: at maximum material condition the feature must fit within a perfect boundary of its MMC size unless the drawing adds a separate form tolerance.

Micrometer resolution

A 0-1 inch micrometer with 40 threads per inch advances 0.025 inch per revolution; a 25-division thimble reads 0.001 inch and a vernier sleeve adds 0.0001 inch.

Sine bar angle formula

The sine of the angle equals gage block stack height divided by the distance between the sine bar rolls; a 5-inch bar with a 0.5000 inch stack sets 5.739 degrees.

Gage R&R acceptance

Percent study variation under 10 percent is acceptable, 10 to 30 percent is marginal and may be accepted for non-critical work, and over 30 percent requires improvement.

Three-wire measurement

For 60-degree threads the over-wire dimension equals pitch diameter plus three wire diameters minus 0.86603 times the pitch, giving the thread pitch diameter.

Surface feet per minute

Cutting speed measured at the tool's outer edge; RPM equals 3.82 times SFM divided by cutter diameter in inches, so required RPM rises as diameter shrinks.

Chip load per tooth

The thickness of material each cutting edge removes per revolution, used to calculate feed rate as RPM times number of teeth times chip load.

Built-up edge

Work material welded to the cutting edge during low-speed, high-feed cutting; it breaks away and damages the finish and is eliminated by higher speed or better coolant.

Work hardening

Stainless steels and nickel alloys harden when a tool rubs instead of cuts, so constant feed and depths below the hardened skin are required to avoid tool failure.

G43 tool length compensation

The G-code that applies the tool length offset stored in the H register, shifting the Z axis so programmed Z values measure from the tool tip.

G41 cutter compensation

The G-code that offsets the tool path to the left of the programmed direction by the radius in the D register, allowing the part to be programmed to print dimensions.

G83 peck drilling cycle

A canned cycle that drills in increments of the Q value and retracts fully to clear chips between pecks, used for holes deeper than about three diameters.

CAM post processor

Software that translates a CAM system's toolpath output into the specific G-code dialect of a machine control, including arc, tool change, and canned cycle formats.

Tool length offset

The distance from the machine gage line or reference surface to the tool tip, stored in the offset page and applied by G43 during machining.

3-2-1 locating principle

A workholding rule that removes all six degrees of freedom using three points on the primary plane, two on the secondary, and one on the tertiary.

Soft jaws

Aluminum or mild-steel jaws bored in place while clamped at the part diameter, giving full contact and concentricity without marking the workpiece.

Climb milling

Milling where the cutter rotates into the feed direction, starting with a thick chip and ending thin; it improves finish and requires an axis with low backlash.

Cpk

A process capability index equal to the smaller distance from the process mean to either specification limit divided by three standard deviations; 1.33 or higher is typical.

Overall equipment effectiveness

The product of availability, performance, and quality, measuring how much of the scheduled time produced good parts at the rated cycle speed.

M01 optional stop

A program stop that halts the machine only when the optional stop switch is enabled, used to check the part or insert a manual operation.

First article inspection

A full dimensional verification of the first production part against every drawing characteristic, performed before the run is released for production.

Backlash

Lost motion when an axis reverses direction, caused by wear or clearance in the ball screw, thrust bearings, or coupling, and visible when indicating a part.

Five Whys

A root-cause technique that repeatedly asks why a problem occurred until the underlying process failure, rather than a symptom, is identified.

Pareto analysis

Ranking problem causes by frequency or cost so the few causes producing most of the defects are addressed first.

Way lube system

A pump that delivers metered oil to slideways and ball screws; alarms indicate an empty reservoir, broken line, or failed metering unit, not just low oil.