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Remember, Inspection Is Work Versus Risk
(In accordance with Y14.5M-1994 standard)

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Everywhere I go I find people who think that the part must be inspected better when GD&T is used. Although we talk about 100% inspection, it never really happens. This example shows two ways to tolerance the thickness of a block. How can anyone declare that because a profile of a surface tolerance is used, the part must be inspected more closely? The + tolerance requires making certain that no two point measurements are less than .990. For the profile of a surface, all points are to be within .010 of the BASIC goal of 1.000. In both cases it would not be practical to contact all points on the surface. Therefore, enough points are checked to be confident the parts are good. The more points checked, the greater the confidence. In other words, it’s work versus risk, regardless of how the requirement is specified.

Back to Tips Tip added Oct 1999