10% Product Tolerance Rule ASME B89.1.5:1998 p 4.1

The 10% product tolerance rule is commonly used in the manufacturing industry. It is considered a "rule-of-thumb" which means that it is a suggestion or a starting point. You, as the engineer, may use the 10% product tolerance rule, or deviate from the 10% product tolerance rule, as long as you can justify your decision to your management.

To calculate the gage tolerance using the 10% product tolerance rule:
1. Calculate the full tolerance of the product feature.
2. Calculate 10% of the product feature tolerance to find the full gage tolerance.
3. Divide the full gage tolerance in half to find the gage member tolerance.
(Otherwise stated: Product Tolerance x 0.05 = Gage Member Tolerance)

Standards that relate to gage design decisions:
ASME B89.7.3.1 Guidelines for Decision Rules: Considering Measurement Uncertainty Determining Conformance to Specifications
ASME B89.1.5 Measurement of Plain External Diameters for use as Master Discs or Cylindrical Plug Gages
ASME B89.1.6 Measurement of Plain Internal Diameters for use as a Master Rings or Ring Gages
These standards are available for purchase from ASME