Projected Tolerance Zone – Where It Should Be Used - GDT
When specifying a threaded hole or a hole for a press fit pin, the orientation of the hole determines the orientation of the mating pin. Although the location and orientation of the hole and the location of the pin will be controlled by the tolerance zone of the hole, the orientation of the pin outside the hole cannot be guaranteed, as shown in Figure The most convenient way to control the orientation of the pin outside the hole is to project the tolerance zone into the mating part.
The tolerance zone must be projected on the same side and at the greatest height of the mating part. The height of the tolerance zone is equal to or greater than the thickest mating part or tallest stud or pin after installation. In other words, the tolerance zone height is specified to be at least as tall as the MMC thickness of the mating part or the maximum height of the installed stud or pin. The dimension of the tolerance zone height is specified as a minimum.