When you’re building something with screws, knowing the right length is critical to the project’s success. If the screw is too long, it will protrude through the material and can cause damage. On the other hand, a screw that’s too short will not reach the intended fastening location and may not be strong enough to hold anything in place. The best way to figure out the correct length is to consult a screw size chart. However, many of these charts are written with metric measurements, and it’s not always easy to translate them back into inch-based measurements. The article below provides a simple solution: a chart that lists the equivalency between screw gauges (diameters) and decimal inches, as well as their millimeter equivalents.
This chart is the perfect tool for deciphering the confusing world of metric screws and other non-standard fasteners. It also lists the corresponding drill sizes for a given screw gauge. For example, a #10 screw will have a major diameter of 3/16 inches and is commonly available in lengths between 3/4-inch to 6-inches. This type of screw is designed for light wood construction and should not be used in masonry applications, which require a masonry plug or lag shield.
The first number on a screw gauge is the major diameter, or screw size. This measurement is sometimes written as a decimal, but the more common practice is to use a number that starts with a zero. A #12 screw, for instance, is 7/32 of an inch in diameter and is most commonly found in lengths between 3/4-inch and 4-inches. This size of screw is ideal for general construction projects.
Next, the chart identifies the screw’s thread series. Screws with coarse threading are typically labeled with a “UNC” designation, while those with fine threads are referred to as “UNF.” The final number on the chart is the screw’s thread pitch, which is the average number of thread peaks that fit within one inch of screw length. Depending on the screw’s gauge and thread series, the thread pitch may be designated with a hyphen or without.
If the screw is from the coarse series, it will have a higher thread count and, therefore, a larger screw diameter than one from the fine series. For example, a #10 screw has a coarse thread and 16 threads per inch, while a #8 screw has a fine thread and 12 threads per inch.
The next time you’re at the hardware store, you’ll be able to quickly determine which type of screw you need by looking at the chart. Just remember to double-check the major diameter, or screw size, and the number of threads per inch to make sure you’re getting the right fasteners for your project. With this helpful tool, you’ll be able to save yourself a trip to the hardware store and ensure that your work is completed on time. Good luck! #12 screw diameter