Fri. Feb 23rd, 2024

Screws come in a variety of sizes and shapes for an endless number of construction tasks. Choosing the right screw for the job is vital to its long-term strength and effectiveness. But measuring a screw can be more complicated than it appears. There are three key measurements every tradesperson needs to know: gauge, threads per inch (TPI) and length.

The imperial system measures screw threads and lengths in inches, while the metric system uses millimeters. To measure a screw’s diameter, you can use a tape measure or ruler, but a caliper is the best tool for accurate results. To determine the threads per inch, or TPI, you count the number of thread peaks along a one-inch length of the screw. A screw with coarse threads will have more peaks than a fine thread screw, which has fewer peaks.

In the US, screw size is often identified by two numbers in a standardized format: the major diameter and the threads per inch. These dimensions are commonly found on a screw’s packaging. The first number is the screw’s gauge, while the second is its TPI. For example, a screw with a major diameter of 1/4″ and a TPI of 20 is considered a size #8 screw.

Screws are also categorized by the way they’re made. Traditional subtractive methods include cutting, forming and molding, while newer additive techniques can produce various forms of threads. The threads can also be sorted into different types, including standard, fine, or coarse, and stepped up or down to increase or decrease their pitch. 3/8 inch to mm

By Admin

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