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Measure Normal to the Surface
(In accordance with Y14.5M-1994 standard)

PDF of this Tip

When measuring nearly every geometric control, the indicator or CMM probe should move normal (at 90°) to the surface. The exception is circularity when applied to a conical surface. Circularity requires that the movement be in a plane normal to the axis rather than the surface. If the movement for other geometric controls is not normal to the surface, a sine or cosine correction should be made. For the profile of a surface control which is applicable to the 2X R8 corners shown on the drawing, once the datums are established, the part may be rotated about the basic location of the radii while the indicator remains normal to the surface.

Back to Tips Tip added Aug 2002