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Simplify Your GD&T
(In accordance with Y14.5M-1994 standard)

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Consider revising your general title block tolerance! You can clean up the drawing and move toward the new technology of minimally dimensioned or dimensionless drawings. As companies mature with Geometric Dimensioning and Tolerancing, more and more of the dimensions on a drawing need to be basic dimensions. Basic dimensions are used to indicate the desired location or orientation of features. These basic dimensions indicate the ideal geometry of the part and are not toleranced. The tolerance applies to the features that are located or oriented by the basic dimensions. In other words, any basic dimensions or dimensions with a tolerance specified on the drawing do not use the general title block tolerances. On this drawing, for example, none of the dimensions shown use the general tolerances.

A better approach is shown on the revised drawing below. By stating that ALL UNTOLERANCED DIMENSIONS ARE BASIC and specifying a general profile tolerance relative to a datum reference frame, several improvements have been made to the drawing.

Many companies have taken the next step which is to have dimensionless or minimally dimensioned drawings by making the CAD model BASIC with a general profile tolerance and only specifying datums, position tolerances on features of size and tighter profile tolerances where needed on the drawing or CAD file.

Back to Tips Tip added Jan 1998