What might be a reason to use a composite tolerance on a well cap or plug feature?

• A. To control multiple related features relative to multiple datums more efficiently.
• B. To strictly limit one feature at a time.
• C. To eliminate datums from consideration.
• D. To simplify measurement by ignoring form.

Answer: (A)

Composite tolerancing is used when you need to control the location of several related features with respect to more than one datum, using a single tolerance frame. For a well cap or plug, there are multiple features whose positions must stay coordinated to fit and seat correctly against a set of datums. Applying a composite tolerance lets you express all those relationships together, making both manufacturing and measurement more efficient because one tolerance frame governs how those features relate to the datum set rather than creating separate controls for each feature.

Trying to limit just one feature at a time would require multiple separate tolerances and wouldn’t capture the needed interrelationship among the features and datums. Datums aren’t eliminated by a composite tolerance; they define the reference frame the part must relate to. And a composite tolerance isn’t about ignoring form—it governs location relative to datums, while form might be controlled by other, separate tolerances if needed.