Measurement of Screw Thread Profile

The screw thread profile in addition to pitch and lead should be measured in order to know the screw thread contact condition which has an important role at driving performance of lead-screw. This paper describes two measuring methods of screw thread profile excepting the cross section profile included the center line. At first the cross section profile which is parallel to center line is measured. By this method the wider area accuracy of screw thread profile can be known in comparison with the measuring method of cross section profile included center line. Next the cross section profile perpendicular to center line is measured. In this method about half area profile of screw thread of the former method is known. But in the later method, the screw thread displacement of center line direction is performed accurately, because it is done with revolution of screw. And the error which happens followed the origin setting of feeler becomes small also. So more accurate measurement can be done easily by later method. The reproducible results are gained under actual measurement by these two methods.