A projected tolerance zone is used in GD&T to control tolerances for features that engage with a mating part over a projected distance above the surface.

A projected tolerance zone is used in GD&T to control tolerances for features that engage with a mating part over a projected distance above the surface.

• A. A projected tolerance zone is used in GD&T to control tolerances for features that engage with a mating part over a projected distance above the surface.
• B. A projected tolerance zone is used to ensure tolerances are only applied at the surface.
• C. A projected tolerance zone is used when the feature does not engage any mating part.
• D. A projected tolerance zone is used when the feature is perfectly machined.

Answer: (A)

A projected tolerance zone controls how a feature’s position is guaranteed not just at the surface, but along a defined distance as it would engage with a mating part. When a feature like a locating pin, stud, or threaded fastener enters or protrudes into another part, the clearance and alignment must hold not only where the feature meets the surface but along the entire engagement length. By projecting the tolerance zone above the surface by a specified height, the GD&T specification ensures the axis (and sometimes orientation) remains within tolerance throughout that engagement, preventing interference or misalignment as the parts come together. This is essential for assemblies where parts interact over a length of contact, not just at the immediate surface.

A projected tolerance zone controls how a feature’s position is guaranteed not just at the surface, but along a defined distance as it would engage with a mating part. When a feature like a locating pin, stud, or threaded fastener enters or protrudes into another part, the clearance and alignment must hold not only where the feature meets the surface but along the entire engagement length. By projecting the tolerance zone above the surface by a specified height, the GD&T specification ensures the axis (and sometimes orientation) remains within tolerance throughout that engagement, preventing interference or misalignment as the parts come together. This is essential for assemblies where parts interact over a length of contact, not just at the immediate surface.