Screws are a staple in almost any home improvement project and having the right size and type of screws for each job makes all the difference. They are strong, durable and provide a secure hold when used in the proper materials. They come in a variety of shapes and sizes and with varying thread patterns designed for use on wood, drywall, sheet metal and concrete, among other things. In addition, they have a wide range of heads including Phillips-head, slot-head, pan-head and Torx-head.
In the United States, most screws are listed in a system called Unified Thread Standards (UTS). A UTS screw is labeled with three numbers: the gauge size, the number of threads per inch and the shaft length in inches. For example, a 6-32 screw means it has a #6 diameter, 32 threads per inch and is an inch and a half long. In the late 19th century, engineers began standardizing thread profiles and sizes to ensure reliable interchangeability.
Metric screws are becoming increasingly popular around the world and are slowly displacing older inch-based systems. In Austrlia, most screws are listed in metric and have the following equivalant measurements:
To measure a screw’s gauge size, find a screw with a known major diameter and use a caliper to determine the screw’s length at that point. To measure the threads per inch, simply count the number of thread peaks along a one-inch length. If you’re not sure which measurement to use, Engineering Toolbox has a great table that shows UTS screw sizes and their decimal equivalents. 2 in to mm