CNC TRUECUT / MACHINING REFERENCE
GD&T position and dimensional inspection
Understand the difference between a coordinate position calculation and complete drawing-based GD&T inspection.
What a coordinate position calculation tells you
For a two-dimensional nominal centre, subtract nominal X and Y from measured X and Y. The centre’s radial offset is the length of that error vector. When the tolerance zone is expressed as a diameter, the coordinate error is twice the radial offset. The true position tool performs this arithmetic and compares it with the entered diameter.
What the calculation does not establish
The numerical offset alone does not simulate a datum reference frame, establish orientation over feature length, or apply material-condition modifiers. A measured hole can satisfy a coordinate check while failing another drawing requirement. Confirm the measurement method, datum setup and complete feature control frame before drawing an acceptance conclusion.
Position, size and fits
Size limits describe the permissible feature size. Position controls where a feature is allowed to lie relative to a datum framework. The hole and shaft limits tool calculates clearance or interference from entered size limits, but it does not replace position inspection or derive an ISO tolerance grade.
Use the specified edition
Apply the edition and interpretation required by the drawing, customer or quality system. General shop explanations cannot replace the complete governing standard. See ASME Y14.5 for the standard’s official publication information.