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If You Do Not Like a Rule - Override It!
(In accordance with the ASME Y14.5-2009 standard)

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There are many default rules found in Section 1.4 of the Y14.5 standard. When you reference Y14.5 on a drawing, you invoke these rules. If you do not want a rule to apply, you must do something overt on the drawing to override the rule. For example, in Section 1.4 Fundamental Rules, (m) of the ASME Y14.5-2009 standard we are told that “Unless otherwise specified, all dimensions and tolerances apply in a free-state condition.” In other words, the part is considered to be rigid. You cannot distort the part during verification. This is the default. However, for parts that deform easily or will be deformed at assembly, it would be better to have the tolerances apply where the part is restrained in some way. This is specified by adding a note to the drawing which describes how the part is to be restrained when the part is inspected. Such a note indicates that the part is considered to be non-rigid and that it can be deformed in some way. The note might specify how to restrain the part with a force, to a dimension, while in a specific orientation, etc. Many stamped sheet metal parts and plastic parts should include such a note. On this drawing the restraint note tells how and where to apply force when inspecting the part. All of the tolerances apply with the part in this restrained condition except for the profile of a surface tolerance on the primary datum feature. This tolerance applies in the free state without any restraint.

Back to Tips Tip added Oct 2011