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Use Profile of a Surface Because it is Easy to Measure
(In accordance with Y14.5M-1994 standard)

PDF of this Tip

To dispell the huge misconception that profile of a surface is hard to measure, this series of Tips illustrates how easy measurement of profile of a surface really is. The surface located by the R12.7mm dimension is controlled by the general profile tolerance relative to datums A, B and C. Since the R12.7mm dimension is BASIC, the indicator would be mastered at 12.7mm relative datum axis B established by the gage pin shown. When the part is rotated about the gage pin, the indicator may not vary more than ±0.75 (half the total profile tolerance). What could be simpler?

On a CMM, the operator would take polar measurements relative to datum feature B. In this illustration the part is not maintaining full contact with datum A simulator. This will introduce a small amount of measurement uncertainty. If measurements of the radius indicate that it is marginally inside the tolerance zone, better simulation of A should be considered. There is always uncertainty when measuring. It just has to be understood and accounted for.

Back to Tips Tip added Aug 2004