ASME Y14.5-2018, “Dimensioning and Tolerancing,” Section 2.9 states that “each tolerance of orientation and datum reference for a screw thread applies to the axis of the thread derived from the pitch cylinder.”
Spence Industries, Inc. offers the best gage on the market for determining basic position and orientation of threaded holes. With a calibrated pitch cylinder and longest standard projected tolerance zone, JO-PLUGS® provide positive quality results with repeatability and reproducibility.