How To Measure Thread Size With Caliper. The threads of a used fitting can become worn and distorted, so the measurements may not be exact. You insert the screw in the caliper as shown in the photos above.
2.) second, use a thread pitch gauge to identify the number of threads per inch. Thread dimensions are based on the id of the pipe. For example a thread pitch of 1.5 means that the distance between one thread and the next is 1.5mm.
For metric connections, measure the distance between threads.
Caliper to measure the thread diameter. In the english system, the thread size and pitch (number of threads per inch) are given, along with the thread type. Measure any full thread corridor; Measure the thread diameter with your caliper.