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

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Use the new free state symbol for your plastic, sheet metal and other flexible parts. In section 1.4 FUNDAMENTAL RULES of Y14.5, paragraph (l) tells us that "All dimensions and tolerances apply in a free state condition. This principle does not apply to nonrigid parts as defined in paras. 2.7.1.3(b) and 6.8." The default, then, is that all parts are considered rigid unless there is some indication that the part may be flexed or distorted for inspection. A way to indicate that a part is not rigid is to add a constraint note. If some tolerances are to be checked with the part not constrained, the new free state symbol may be added to specific tolerances. Many useable sheet metal and plastic parts will pass inspection and be functional if clamped to a condition that simulates the assembled or functional state. Usually when a constraint note is applied to a drawing, at least one tolerance should be inspected in the free state to limit the free state variation. In this example the entire part is inspected with the part constrained except for the flatness spec which would be checked unrestrained in the free state.

Back to Tips Tip added Jan 1999