What is a projected tolerance zone used for?

• A. To measure surface roughness on a feature.
• B. To adjust tolerances during manufacturing.
• C. To control wear on mates during operation.
• D. To account for parts that must align with or pass through another part at some projection height.

Answer: (D)

A projected tolerance zone is used when a feature must be aligned or pass through another part at a certain depth above the surface. By projecting the tolerance zone to a specified height, the positional control applies not just at the surface but through the depth where the mating part interacts. This ensures that, during assembly, the features—like pins, studs, or holes—line up and fit correctly as they extend into or through the mating part, preventing interference or misalignment.

The other ideas don’t fit this purpose. Measuring surface roughness relates to texture, not where a feature must stay within a positional tolerance during assembly. Adjusting tolerances during manufacturing isn’t what the projection does. Controlling wear is a functional consideration, but the projected zone specifically ensures proper alignment through a defined projection height.