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Is a true position tolerance a round zone or a square one?

Last updated 10 August 2026

Round. The diameter symbol in the second compartment is what makes the zone cylindrical, and it is not decorative.

A position tolerance of .010 on a hole does not permit five thousandths of error in X and another five in Y. It says the axis has to fall inside a cylinder .010 across, centered on true position. The corner of the square that a coordinate reading describes sits about forty percent further out than the cylinder allows.

This is the most consistently misread callout in production, and it fails in the dangerous direction: machinists who came up on plus and minus tolerancing check position by reading X and Y deviation separately, and pass holes that are out.

Worked

The frame	⌖\|⌀0.01\|A
Control	Position
Family	Location control
Datum reference	required
Diametral zone	allowed
Material condition modifier	allowed
Legal under ASME Y14.5-2018	yes

Nothing in this frame contradicts Y14.5-2018. That is not the same as it being the right control for the job, the right datums, or a tolerance the process can hold.

Open this case in the calculator, and change the numbers.

Computed by ctrlPlanner. ASME Y14.5-2018.