Master Task Group 142 Tolerances 2026 – Precision Practice for Future Proficiency!

A projected tolerance zone is about extending the controlled area of a feature beyond the surface so the tolerance applies at the depth where the mating part actually engages. When you project the tolerance zone, you specify a height, and the position (or other) tolerance is measured at that projection. This means the part must be within tolerance not just at the feature’s surface, but at the height where the mating part will interact, ensuring there’s enough clearance for assembly even if there are variation along that depth.

In practice, this helps prevent interference from misalignment or part variation at the engagement depth, which is critical when studs, pins, or protruding features enter a hole or mate with another feature. The projected zone doesn’t erase datum references or fix the hole’s location regardless of assembly, and it doesn’t reduce the tolerance to zero—the tolerance is simply extended along the projection height to match the actual assembly condition.