Pitch Diameter Measurement of Threaded Gages Using a CMM
Ralph C. Veale, Edgar G. Erber, Bruce R. Borchardt
The reference datum for a screw thread is the pitch diameter cylinder. Although a defined method within the United states for pitch diameter measurement exists, it does not follow worldwide procedures, and the complexity and uncertainties associated with this measurement often go unappreciated. Some of the problems associated with using a coordinate measuring machine (CMM) for measurements on both external and internal threads are discussed.