What is the best tool for determining the threads per inch of a bolt or screw?

The best tool for determining the threads per inch of a bolt or screw is the thread tool gauge. This tool is specifically designed to measure the pitch of the threads accurately, which is essential for identifying the thread count of a fastener. A thread tool gauge typically features a series of notches that correspond to different thread sizes, allowing for precise comparison with the bolt or screw in question.

Using this gauge ensures that the measurement is clear and ensures compatibility with nuts or other fasteners. While a caliper can measure the diameter and overall length of a bolt or screw, it does not provide the accurate thread pitch measurement necessary for determining threads per inch. A screwdriver is designed for driving screws and does not offer any measurement capability. Similarly, a wrench is intended for turning nuts and bolts and is not equipped for measuring thread characteristics. Therefore, the thread tool gauge is the most effective option for this specific purpose.