How to Read a Screw Size
Screws are used to fasten and hold a variety of materials together. The size of a screw is determined by its diameter and threads. It’s important to know how to determine what size screw you need to use for a given job and material, as using the wrong type can damage or weaken it. Screws come in a wide range of sizes and styles, from simple wood screws to specialty screws for plastic or electronics projects. There are also different head types such as rounded heads or oval countersunk heads.
Understanding how to read a screw size will save you time and money when purchasing new fasteners. Screws are typically marked with a gauge number, shaft length in inches and threads per inch. A common example is a 3/8″-16 screw. The “3/8” refers to the diameter of the screw (also called major diameter) and the “16” refers to how many threads are molded into the end of the screw. The number of threads per inch will vary by screw type and material, but in general the higher the thread count, the more secure the screw will be.
The first number on a screw is the gauge, which is a measurement of the diameter of the screw’s major thread. Screws with a major diameter of less than a quarter inch are typically labeled in sizes from #0 to #12, and as the size increases, so does the gauge number and decimal equivalent.
After the American Standard Whitworth design was adopted in 1841, several other standards emerged. Some evolved into national or quasi-national standards, and others were abandoned in favor of Sellers thread, which standardized the overall thread profile as 60deg with a flattened tip.
Screws can have either imperial or metric systems of measurement, and it’s important to understand how each relates to the other when determining what kind to purchase. The imperial system uses numbers from 1 to 20 to rank screw size, and the metric system uses decimal values in millimeters.
Knowing how to read a screw size is an essential skill for professional and home DIYers alike. Knowing your screw gauge, thread size and length will help you find the right fasteners for your materials and make sure that they have a firm grip without bending or breaking. It’s also helpful to know what kinds of heads are available, as some are more useful for specific applications than others. Screws can be purchased individually or in packs of varying sizes, and it’s usually best to buy trade packs if you work with screws often. This way, you’ll be able to keep track of your inventory and easily swap out old screws for new ones when necessary. Jaycon Systems has a wide selection of screws in stock, from small plastic screw nuts to multi-packs of metal screws for electronics and plastic fabrication. Contact us for more information or to place an order. We offer same day shipping for most orders and have a 100% satisfaction guarantee on all of our products. 1/4 to mm