Inspecting a mechanical chamfer, and its limits
On the design drawing of a bearing entry bore, the edge break calls for a lead-in chamfer dimensioned 1.5 x 45°. The machining inspector has to check the axial width of the chamfer and its angle, to make sure the bearing ring slides in without marking the metal.
Methods and tolerances for inspecting a chamfer
| Chamfer size | General tolerance ISO 2768-m | Recommended inspection means |
|---|---|---|
| Over 0.5 up to 3 mm | ±0.2 mm / ±1° | Chamfer gauge / profile projector |
| Over 3 up to 6 mm | ±0.5 mm / ±30’ | Caliper with bevelled jaws |
| Over 6 mm | ±1.0 mm / ±20’ | Angle gauge + dial indicator |
All values are given for the reference environmental conditions of 20 °C.
Measuring with an optical gauge or a profile projector
A small chamfer (e.g. 0.5 x 45°) is measured accurately on an optical profile projector at 20x magnification. The operator measures the axial width and the angle relative to the locating face. To go back over the applicable general tolerances, read our piece on the ISO 2768-mK tolerance at 250 mm.
Turning lead-in chamfer dimensions into numerical limits
A chamfer dimensioned 1.5 ±0.2 x 45° ±1° allows a width between 1.3 mm and 1.7 mm and an angle between 44° and 46°. The cutting tool should be set to the middle of that interval.
Example: inspecting a fitting body
Chamfer dimensioned 2.0 x 45° under ISO 2768-m. Projector reading: width = 2.35 mm, angle = 45.2°. 1. ISO 2768-m tolerance (0.5 to 3 mm): ±0.2 mm. 2. Allowed limits: [1.8 mm; 2.2 mm]. Verdict: the measured width (2.35 mm) exceeds the limit by 0.15 mm. The chamfer is too deep, and the part is declared non-conforming.
Classic pitfalls when measuring chamfers
The first pitfall is using a caliper whose jaw doesn’t reach the bottom of the blend radius. The second comes from confusing the leg length with the hypotenuse length. The third is forgetting the burrs along the chamfer edge. To make your metrology readings reliable, use CoteCote and its technical support.