GD&T Symbol Guide
Projected Tolerance Zone
Extends a tolerance zone beyond the feature surface to protect fastener clearance in assembly.
Definition
The projected tolerance zone symbol evaluates the controlled axis beyond the physical depth of the feature.
It is most common on threaded holes or pins where orientation error can cause interference in a mating part.
Application
Use it when a fastener must pass through a mating part whose thickness magnifies hole-axis tilt.
The projected height may be shown in the feature control frame or as a dimensioned projected zone on the drawing.
Projected Tolerance Zone Drawing Use
Projected Tolerance Zone is read with the adjacent dimension, note, or feature control frame so inspection uses the intended feature definition.
3D Tolerance Zone
This modifier changes how a related dimension, note, or feature control frame is interpreted.
Inspection Method
Read the symbol with the attached dimension, note, or feature control frame before evaluating the feature.
Verify the controlled feature using the drawing's stated limits, datum setup, and any special notes tied to the symbol.
Worked Read: Projected Tolerance Zone
A drawing includes the Projected Tolerance Zone symbol with a related feature requirement.
Identify
P
Recognize the Projected Tolerance Zone symbol and the feature it modifies.
Read
Adjacent value
Use the attached dimension, note, or frame cells as the controlling requirement.
Inspect
Per drawing
Measure the named feature using the specified interpretation rather than assuming a generic size check.
Projected Tolerance Zone clarifies how the feature is defined so the drawing and inspection method stay aligned.
Comparison Table
| Item | Controls | Typical Placement |
|---|---|---|
| Projected Tolerance Zone | Requirement interpretation | Next to a dimension, note, or frame |
| GD&T control | Geometric variation | Feature control frame |
| Datum reference | Measurement setup | Datum feature or frame cell |
Notes
This page is part of the drawing-symbol reference set rather than a standalone geometric tolerance category.
When the symbol modifies a feature control frame, read it together with the tolerance value and datum references.