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Where Profile Is Applied to Features of Size, You Count it Twice
(In accordance with Y14.5M-1994 standard)

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This seems to throw folks every time. First, as you look at the drawing, you will notice that the profile tolerance is not associated with the basic dimension of 60 mm. Often I will see a profile tolerance next to a dimension which is totally wrong. Unless it is being used as a general tolerance, the profile tolerance must be directed at the surface being controlled as you see here.

If you were to measure the size of the hole with something like a caliper, you would be contacting two surfaces. Therefore, the variation you measure could be as much as twice the profile tolerance. Even though the diameter of the hole is dimensioned, it is really the radius that has the profile tolerance. In this case, the diameter of 60 mm could be as small as 59.6 mm or as large as 60.4 mm.

Back to Tips Tip added May 2006