In any fastening project, the right screw is crucial to a secure connection and successful completion of the task. Accurately identifying the correct screw size is the first step in ensuring that the screw fits properly without damaging the material it’s being installed into. While basic rulers and tape measures are effective for some applications, calipers provide a higher level of precision in this type of measurement, making it easier to ensure that you’re getting accurate measurements.
The diameter of a screw is its widest point and is typically expressed in millimeters (mm) for Metric screw sizes, or inches (in) for Imperial screw sizes. When measuring the diameter, make sure to avoid the threads of the screw to get a precise reading.
A screw’s thread size is indicated by a gauge number, which refers to its major diameter. This is measured from the crest of one side of the screw to the crest on the other side. A smaller number indicates a coarser thread, while a larger number is indicative of a finer thread. In addition to a specific number, screw sizes also have a shortened name known as a nominal diameter that simply refers to the major diameter.
Length is another important factor to consider when identifying the proper screw size. This is the distance from the tip of the screw to the underside of the head, or for screws that have no head such as countersunk heads, from where the oval top rests on the surface of the material. screw diameters