What tool is recommended to determine the size of a screw?

The recommended tool for determining the size of a screw is the screw checker. This tool is specifically designed to help identify various screw sizes and types quickly and accurately. A screw checker typically features cutouts or openings sized for different screw heads and shank diameters, allowing users to easily match the screw in question to the correct size.

The advantage of using a screw checker lies in its simplicity and speed for identifying sizes without the need for precise measurements, which can be particularly useful in settings such as firearms inspection where quick, accurate identification is important.

Other tools mentioned, while useful in their own right, serve different purposes. For instance, a magnetic screw gauge is generally used to assess the magnetic properties of screws rather than their size. A caliper tool is great for measuring dimensions precisely, but may require more time and skill to use effectively for screw dimensions specifically. Lastly, a thread pitch gauge is essential for measuring the pitch of screw threads, but it does not provide direct information about the overall size or diameter of the screw itself. Thus, for straightforward identification of screw size, the screw checker is the most suitable choice.