Screws are used for a variety of different tasks and come in many shapes and sizes to suit the material being worked on, its thickness and strength. Choosing the correct screw for the job is essential to ensure it will hold the load, and won’t damage or degrade over time. It’s also important to make sure the screw fits the hole so it is securely inserted. The wrong size screw can compromise the integrity of the work, and lead to a weak or broken connection. It can also cause damage or protrude through the material, posing a safety risk.
Measuring screw diameter is easy and can be done with a simple ruler or tape measure, but a caliper is the preferred tool for high-precision measurements. The caliper can measure the major diameter and thread pitch of the screw, giving you a comprehensive understanding of the dimensions of the fastener.
Screws are often labeled with their gauge, length and head size in imperial or metric systems. Most wood screws have the shaft measurement (length) listed first, followed by the gauge and threads per inch. The gauge is the diameter of the screw, and the threads per inch is the number of peaks on one side of the screw. A screw with a thread count of 32 is a #6 diameter, and 1 1/2″ long. Some screw manufacturers include the threads per inch in the gauge number, while others don’t. A screw with a thread count of 35 is a #10 gauge, and 2″ long. 5/16 lag bolt pilot hole