A novel system for automatic measurement and inspection of parallel screw threads

Because of the importance of screw threads in machine elements, screw thread measurement and inspection has been debated extensively for more than 20 years. There are about 30 separate geometrical features and dimensional characteristics in the design and construction of screw threads. Therefore many methods have been developed for measuring and inspecting these features. Most of these methods are limited to measuring or inspecting a small number of features. In this paper, a novel system has been developed, using a Measurescope, personal computer and developed software, for measuring and inspecting most of the common types of screw thread. The system is capable of measuring the most common features of screw threads (16 features). Repeatability of measurements is also provided to obtain accurate measurements and useful statistical parameters. In addition, the system is capable of inspecting threads based on a reference thread and given tolerances for the measured features. The traceability process and the uncertainty budget of the developed system are presented. The developed software, named AutoMIST, is fully written in house using Microsoft Visual C++ 6.0 and it is ready to run on any Windows environment.