Whether you’re working with wood, metal or even PVC there are a wide variety of screw sizes that can be used for different applications. Choosing the right screw size is essential to ensure that it will efficiently anchor into or hold on to whatever material it’s being screwed into. Screws are typically described by their gauge, threads per inch and shaft length. They may also be referred to as imperial or metric depending on how they are labeled.
The first number on the screw is referred to as the gauge, which is the basic size of the outer threads in inches. The higher the gauge number, the narrower the threads are. The second number on a screw is the threads per inch, which refers to how many threads are in one inch of the screw’s diameter. This number is usually given in decimal form with the smallest fraction being zero and the largest being twelve.
The third number on a screw is the shaft length in inches, which is determined by the thickness of the material that it will be screwing into. Thicker materials generally require longer screws than thinner ones to ensure a proper fit and secure hold.
Knowing how to read a screw size can help you determine the correct size for a project, and can save you time in searching through a bag of screws for the right one. The good news is that measuring the size of a screw is easy and can be done with a simple ruler or measuring tape and a screw gauge guide. pilot hole for 3/8 lag screw