Screws can add a lot of strength to a project and help hold materials securely. But choosing the right size and type is important to avoid tearing or splitting the material. Screws come in a range of sizes and thread patterns designed for different materials like wood, drywall and metal. Screws also come in different head types like Phillips-head, slotted-head, rounded or Torx-head screws. Unlike nails that can become loose over time, screws have a much stronger hold and can enhance the soundness of a structure or building. To ensure that a screw is properly sized for the job, it is important to know three essential measurements: gauge, diameter and length.
Screw dimensions are usually listed on the packaging in the imperial system or in the metric system depending on how they are used in the country of purchase. For example, a package labeled 6-32 indicates that the screw has a thread diameter of 0.063 inches and a length of 0.312 inches from the head.
In the imperial system, screw sizes are described by their gauge number and threads per inch (TPI). The gauge numbers refer to the size of the screw’s major diameter, with higher numbers indicating smaller diameters. The thread pitch is the distance between adjacent screw thread peaks and is the reciprocal of the screw’s gauge number. The length is the screw’s total length from its head to its base, or shank. Screws with a lower thread count are designated as Unified Coarse Thread (UNC), while those with a finer thread pitch are described as Unified Fine Thread (UNF). In the metric system, screw sizes are specified by their diameter in millimeters and length in centimeters. 2 in to mm