True Position
Glossary · Tolerance & Measurement
At a glance
- Category /
- Tolerance & Measurement
- Also called /
- position tolerance
- Related /
- 2 terms
- Source /
- Written in the shop
True position defines a circular zone within which the centre of a hole or feature must fall, measured from the stated datums.
Also called: position tolerance
In practice
Instead of tolerancing a hole location as X ±0.005" and Y ±0.005" — which describes a square zone — true position describes a round zone of a given diameter. It is a more honest description of what a bolt actually needs.
Why it matters
A round tolerance zone is about 57% larger in area than the square one it replaces, so switching to true position often makes a part easier to make without making the assembly any looser.
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