Whether you’re working on a home improvement project, auto repair, or industrial assembly, choosing the right screws for the job is critical to ensure structural integrity and functionality. Getting screw size measurements wrong can lead to a range of issues, from poor holding strength and material degradation to unnecessary waste of time and resources.
In order to choose the correct screw for the task, there are three main factors that need to be taken into consideration: diameter, thread count, and length. These factors can be found in imperial or metric screws and are typically listed in the following format:
The first number is the screw gauge, which refers to the basic outside thread diameter of the screw. This is measured in a system of numbers (ranging from #12 to #0000, super tiny) where each number represents a smaller diameter. Usually, the larger the screw, the higher the gauge number.
The second figure is the thread pitch or TPI. This measures the spacing between threads on a given screw, and is measured in units such as “threads per inch” for imperial fasteners and “twists per millimeter” for metric fasteners.
The third and final factor is the screw length. This is measured from the end of the shank, or shaft, to the tip or blunt end of the head. The length of the screw will determine the depth it will be driven into the material, and it can impact things such as stress loads, material types, and head style preferences. pilot hole for 5/16 lag screw