Screws are a staple of home improvement and many other types of work. They are available in a wide variety of shapes, head-types and sizes. They also come in different thread patterns designed for use on a specific material, such as wood, drywall or sheet metal. Using the proper screw type and size for the job at hand helps prevent damage to materials and improves the speed and ease of project completion. Screw sizing is standardized by both the imperial system (ISO) and the metric system, which uses millimeters (mm). There are several factors that determine a screw’s size: driver type (flat, Phillips or hex), length, shank diameter and threads per inch.
When reading a screw label, the first number represents the screw gauge. Screws are categorized as coarse (UNC) or fine (UNEF). Screws with a major diameter less than 1/4″ are labeled from 0 through 14; anything larger is labeled in fractions of an inch, with the first number representing the gauge and the decimal equivalent shown in the table below.
The next number on a screw label is the number of threads per inch of shaft. Screws are categorized as having coarse or fine threads, with a fine thread having a closer space between them. Screws with a coarse thread are more common and are used for fastening materials that need to be tightened securely, such as sheet metal or concrete. Screws with a fine thread are used for joining materials that need to be held firmly in place, such as drywall or wood.
Finally, the last number on a screw label is the length of the screw. Screws are categorized as short or long. Short screws are for light-duty projects, such as hanging pictures or assembling wooden furniture, and long screws are for heavier tasks, such as building cabinets or making door frames.
If you have an unorganized drawer of loose screws or just need more of the same kind, knowing how to read a screw label can help make sure you get the right size and type. The good news is that measuring and comparing your screws to a screw size chart is easy.
Jaycon Systems engineers use small screws to hold plastic parts and printed circuit boards together. It’s important for us to know how to correctly read screw labels so that we can order the correct fasteners for our projects.
We measure the diameter of a screw by placing it in a thread gauge, which is a strip of metal with various sizes of threads cut into it. We systematically move the screw through the gauge until we find one that matches its size. We then write down that measurement to reference when ordering screw sizes for future projects. Using this method, we can be sure that the right screw is always on hand. If you would like to learn more about Jaycon Systems, please click here to visit our website. You may also contact us with any questions you may have. 1/4 to mm