Measuring Screw Sizes

When using screws, it’s important to have accurate sizing. A screw that’s too small won’t hold properly and can lead to tears in the material. A screw that’s too large can cause the material to split or crack. Measuring screw sizes correctly can help you choose the best fasteners for your job, making them ideal for the materials you work with and ensuring they fit well in the holes you’re drilling into. There are three essential measurements to consider when determining screw size: gauge, threads per inch (TPI) and shaft length in inches.

The gauge of a screw measures the diameter of its external thread. It’s measured from the crest of one side to the crest of the other side and is referred to as the major diameter. A nominal diameter is an estimated major diameter used as a shorthand term that simplifies reference to the measurement.

Screws have a wide variety of heads, from oval head screws to hexagonal head screws. Generally, the head size depends on aesthetic considerations and constraints of the material being worked with. A larger head size may distribute pressure more evenly, increasing holding strength.

The length of a screw refers to the distance from the tip or blunt end of the head to the base or shank. A screw’s length is an important measurement when working with a particular material because it determines how deep the screw must penetrate to maintain a solid hold. pilot hole for 3/8 lag screw