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Position can Control Location of Irregular Features
(In accordance with the ASME Y14.5-2009 standard)

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In the previous tips, we showed an example of using Composite Profile of a Surface to control the location, orientation, size and form of an irregular feature. This type of feature may also use Position to control location and orientation relative to datum references when the size and shape of the feature are defined by a Profile Tolerance. On the drawing below, the Profile of a Surface callout controls the size and form of the hex while the position callout is controlling the location and orientation of the hex.

Since this callout includes the maximum material condition modifier and the BOUNDARY note (Boundary note is optional), a hard gage size at the Maximum Material Boundary (MMB) may be used to inspect the Position control. The only difference between this inspection gage and the one shown in a previous Tip is that the outer boundary need not be checked. Therefore, the NO-GO wire required when Profile of a Surface had been used is not needed. Only the inner boundary has to accept the gage to verify the position requirement.

Position tolerance establishes a theoretical inner boundary shaped identically to the true profile and no portion of the feature is allowed to violate this boundary. This boundary is a 9.8 hex. (10.2 Basic – 0.3 – 0.1 = 9.8).

At MMC, the hex is allowed to move 0.3 total and when it is at LMC (largest hex) it can move 0.5 (includes a 0.2 bonus tolerance).

The figure shown below is a possible gage that might be used to inspect the position tolerance. The values shown are theoretical design values, which do not include gage tolerance and wear allowance.

Back to Tips Tip added Jan 2019