Metrology
Metrology — Wiki
Measuring the part and the machine — tolerances, GD&T, probing and inspection that prove a job is in spec.
17 entries in this group.
- Calibration of Measuring InstrumentsCalibration of measuring instruments compares a tool against a known standard, keeping measurements honest and traceable to a reference.Sep 7, 2026
- CNC Probing & On-Machine MeasurementCNC probing puts a touch probe in the machine's own spindle to set work offsets, measure tools and gauge features between operations, acting on its readings.Sep 7, 2026
- Coordinate Measuring MachineA coordinate measuring machine probes a part in three dimensions, reporting each feature against the drawing for inspection too complex for hand tools.Sep 7, 2026
- Dial Indicators & Test IndicatorsDial indicators and test indicators read small movements on a dial, comparing a surface or axis to the reference it must match.Sep 7, 2026
- Dimensioning ConventionsDimensioning conventions are how a drawing states size and position: the systems, callouts and tolerances a machinist reads.Sep 7, 2026
- First Article InspectionFirst article inspection verifies the first part of a run against every characteristic on the drawing — the proof the process makes the part.Sep 7, 2026
- Fits & Limits (ISO 286)Fits and limits under ISO 286 pair a hole and a shaft tolerance so their assembly is predictable; H7/g6 and the rest name clearance, transition or interference.Sep 7, 2026
- Form TolerancesForm tolerances control a feature's own shape, free of any datum: straightness, flatness, roundness and cylindricity hold a surface true to itself.Sep 7, 2026
- GD&TGD&T is the symbol language that controls how flat, round, positioned and true a feature is relative to datums — tolerance with more meaning than plus-minus.Sep 7, 2026
- General TolerancesGeneral tolerances govern dimensions without an explicit tolerance: the drawing note and ISO 2768 classes set how much untoleranced sizes may vary.Sep 7, 2026
- In-Process vs Post-Process InspectionIn-process vs post-process inspection asks when a part should be measured: during the cut to control it, or after it to accept it.Sep 7, 2026
- Measuring a FeatureMeasuring a feature is matching an instrument to its tolerance; callipers, micrometers, bore gauges and pins each measure their own class of feature.Sep 7, 2026
- Orientation TolerancesOrientation tolerances relate a feature to a datum: parallelism, perpendicularity and angularity hold a face parallel, square or at an angle.Sep 7, 2026
- True PositionTrue position is the location control that pins an axis or centre to a round zone at its true position, from basic dimensions and datums.Sep 7, 2026
- Reading Engineering DrawingsReading engineering drawings is how a machinist turns the drawing into a job: title block, views, dimensions, tolerances and the datums the features hang from.Sep 7, 2026
- Runout TolerancesRunout tolerances limit wobble about a datum axis: circular runout at one cross-section, total runout over the whole surface.Sep 7, 2026
- Surface FinishSurface finish on a machined part is read as Ra and Rz: the averaged and the extreme heights of the surface, taken by a profilometer and set by the cut.Sep 7, 2026