- The thread gauge is a useful tool for identifying the general size of a male or female pipe thread. It only provides a rough thread size; it does not distinguish between different thread types or thread pitches.
- The thread gauge has two sides, one for metric threads and the other for NPT and BSPP/T.
- For internal threads, insert the pointed end of the gauge into the threads. Keep the point as close to the centerline as possible. The internal thread size is the number whose line is contacting the outermost thread.
- For external threads, straddle the threads with the V-shaped end of the gauge. The external thread size is the number whose line is contacting the thread circle.
