A thread wear gauge for coil threads. Coil threads have a nominal new thread profile that offers a substantial load bearing area. The thread wear gauge has a gauging thread with a silhouette that permits it to threadably engage with a coil thread that has been worn so that the shear load bearing area of the thread has been worn away from the coil thread to the point where the coil thread is unsafe for further use. The gauging thread will not threadably engage with the coil thread if the load bearing area has been worn to the point where it is unsafe. The thread wear gauge is a simple, reliable, hand held tool that is capable of being used under field conditions. In use, the thread wear gauge is grasped and manipulated with one hand. An attempt is made to threadably engage the gauging thread on the thread wear gauge with the coil thread that is to be tested. The operator observes whether the gauging thread threadably engages with the coil thread. If it does engage, use of the coil thread is discontinued. The thread wear gauge is equally applicable to internal and external coil threads, and also to concave and convex coil thread profiles.
