True position is the exact, theoretically perfect location of a feature such as a hole, set on a drawing by basic dimensions from datums. A GD&T position tolerance says how far the real feature may sit from that point, usually as a round zone of a stated diameter. On the shop floor, "true position" also means the measured result: twice the distance between the actual and the ideal center. A hole passes when that value is no larger than the tolerance, plus any bonus tolerance the drawing allows.
Example: A hole should sit at X 40.00, Y 25.00 mm from the datums, with a position tolerance of 0.20 mm. The CMM measures it at X 40.06, Y 24.92. The offset is the square root of 0.06² + 0.08², which is 0.10 mm, so true position is 2 × 0.10 = 0.20 mm: exactly at the limit, and acceptable.
Hole location decides whether mating parts bolt together, and a round position zone matches how a round bolt actually fits. Compared with separate plus-or-minus limits on X and Y, it accepts holes that are usable in every direction and gives inspection one clear pass or fail number per hole.
COPLAIN AI PLATFORM
Upload your existing procedures and Coplain AI drafts audit-ready work instructions, job aids and forms from them.
Generate yours automatically with Coplain →Related Tools & Templates