The GD&T Guide
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Location control

Position

What it controls

Position is the most widely used GD&T control for holes, pins, and slots. It defines a zone around the true location where the feature’s axis or center plane must remain. The axis or center plane of a feature of size.

The tolerance zone

How the zone works

For a round hole or pin, position commonly creates a cylindrical zone centered on the true position. The actual axis must remain inside it. For slots and tabs, the zone can be two parallel planes applied to the derived center plane.

Example drawing

See Position on a drawing

Position GD&T example drawing
Position applied to the axis or center plane of a feature of size

Tolerance zone visualized

See the tolerance zone in context

Position illustrated as a cylindrical tolerance zone around a hole axis, located from datums A, B, and C.

Location, orientation, and possible bonus tolerance

Basic dimensions define the exact target location; the position tolerance defines the allowed zone around that target. The datum reference frame orients and locates the zone. A material-condition modifier such as MMC may allow bonus tolerance as a hole becomes larger or a pin becomes smaller, while protecting assembly at the virtual condition.

Example feature control frame

Position feature control frame showing a 0.20 diameter tolerance relative to datums A, B, and C

The indicated hole axis must lie within a ⌀0.20 mm zone located from datums A, B, and C.

Left cellThe geometric control.
Middle cellThe size and shape of the allowed zone.
Right cellsThe datum references establish the inspection setup.

Practical use

When to use Position

Use position for hole patterns, locating pins, slots, fastener features, and other features of size whose ability to assemble matters more than separate X, Y, and angle tolerances.

Inspection

How it is usually measured

Set up the part to its primary, secondary, and tertiary datums in the order shown. A CMM can report the feature axis versus the true-position zone; for repeating production checks, a functional gage can often verify the virtual condition much faster. Be sure the basic dimensions, material modifier, and datum modifiers are part of the inspection plan.

Common mix-up

Position works with basic dimensions. The dimensions locating the true position should be boxed, not given ± tolerances.

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