Classes & Tolerance
Gagemaker tolerance classes per ASME B89.1.5, and the tolerance you surrender to the gauge.
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Gagemaker tolerance by diameter (inch)
Tolerances step up with diameter. Ranges are “above…to”; a boundary size takes the lower row.
| Diameter (in) | XXX | XX | X | Y | Z | ZZ |
|---|---|---|---|---|---|---|
| .010–.825 | .000010 | .000020 | .000040 | .000070 | .0001 | .0002 |
| .825–1.510 | .000015 | .000030 | .000060 | .000090 | .00012 | .00024 |
| 1.510–2.510 | .000020 | .000040 | .000080 | .00012 | .00016 | .00032 |
| 2.510–4.510 | .000025 | .000050 | .0001 | .00015 | .0002 | .0004 |
| 4.510–6.510 | .000033 | .000065 | .00013 | .00019 | .00025 | .0005 |
| 6.510–9.010 | .000040 | .000080 | .00016 | .00024 | .00032 | .00064 |
| 9.010–12.010 | .000050 | .0001 | .0002 | .0003 | .0004 | .0008 |
Surrendering tolerance
Every gauge is paid for in tolerance. In absolute go/no-go gauging, the GO and NO-GO members each tolerance inward, so the headline surrender is GO + NO-GO = 2× the class tolerance (per-member is half). The coarser the gauge, the larger its cut — and you, not the drawing, cover it.
Worked example — Ø1.2390″ ±.0002
Band = .0004″, diameter in the .825–1.510″ row:
| Class | Class tol | Surrender (2×) | % of band | Verdict |
|---|---|---|---|---|
| XX | .000030 | .000060 | 15% | Tight but usable |
| X | .000060 | .000120 | 30% | Heavy |
| ZZ | .00024 | .00048 | 120% | Impossible |
At 15–30% surrender this feature sits at the edge of fixed-limit gauging. If that’s unacceptable, move to variable measurement.