Tolerance Zone Size



This feature control frame specifies the tolerance zone as a circle of diameter .010 at MMC, centered according to the basic dimensions given. The size of the tolerance zone is dependent on the size of the hole.

A feature control frame can specify the size of the tolerance zone at MMC, LMC or RFS (regardless of feature size).

Hole diameter





Tolerance Zone diameter

Determining Tolerance Zone Size

Does this feature meet the true position tolerance?

Basic Dimension True Position

Step 1: What can we measure?

Step 2:

Calculate deviations in x and y directions. How does this compare to the basic dimensions?

Basic Dimension True Position

Step 3: Determining the True Position

Basic Dimension True Position

Tolerance zone, dia. = TZ

Desired position Actual hole center

A hole center that deviates from true position by jc and y lies within a tolerance zone of diameter Z. If Z > TZ, the part is bad.

Co-ordinate Difference

Co-ordinate Difference

Tolerance Perpendicularity

015 014 013 012 Oil 010

008 it Q

True Position and Perpendicularity

True Posistion

This feature control frame specifies the true position tolerance of the hole with respect to 3 datum planes. The order that the datum planes are listed in the feature control frame indicates the priority of each datum. Datums B and C provide reference for the x and y position of the hole center, and datum A controls the perpendicularity of the hole axis .

Referencing datum A means that the center axis of the hole must be perpendicular to datum plane A. The axis must intersect datum plane A inside the tolerance zone

Permissible hole axis variation

Drawing With Positional Tolerancing
.010" wide tolerance zone
+2 -1


  • Goldilocks Hayward
    How to true position tolerance a hole?
    7 years ago
  • richard mckenzie
    What is zone in engineering drawing?
    7 years ago
  • Mewael
    How we calculate hole position tolerances?
    6 years ago
  • sabrina schwartz
    What is tolerance zone in engineering?
    2 years ago
  • Iggi Daniel
    What is tolerance for a hole in engineering drawing?
    8 months ago

Post a comment