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Does a position tolerance always need the diameter symbol?

Last updated 10 August 2026

No. The diameter symbol makes the zone a cylinder, which is right for a hole. Leave it off and the zone is two parallel planes .010 apart, which is what a slot or a width wants.

A round feature is located in two directions at once, so a round zone is the honest shape for it. A slot is located in one direction and free in the other, and a cylindrical zone would be claiming control the design does not need and the process cannot use.

So an absent diameter symbol on a hole is a defect and an absent one on a slot is correct, and no checker can tell them apart because both are legal frames. This is a different question from whether the zone is round or square, which is about reading a callout that already has the symbol on it.

Worked

The frame⌖|0.01|A
ControlPosition
FamilyLocation control
Datum referencerequired
Diametral zoneallowed
Material condition modifierallowed
Legal under ASME Y14.5-2018yes

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

Computed by ctrlPlanner. ASME Y14.5-2018.

This checks one frame. ctrlPlanner keys the whole print, keeps every frame intact through the control plan, and carries them onto the AS9102 forms.

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