GD&T Tips - Dimensions and Tolerances - Direct Tolerancing

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Don’t Forget the Origin Symbol (#43)

(In accordance with the ASME Y14.5-2018 standard)

(In accordance with the ASME Y14.5-2009 standard)

(In accordance with Y14.5M-1994 standard)

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On simple parts the dimension origin symbol may be used very effectively. This bracket mounts on the shorter surface as shown. A lamp is attached to the longer surface. It is desirable to inspect the 38mm dimension by mounting the part on the functional shorter surface. By using the dimension origin symbol, it is required that this dimension be inspected by mounting the bracket on the shorter surface. The same control could be accomplished by calling out the shorter surface as a datum feature and applying a profile of a surface control on the longer surface.