These screws are available in metric and imperial units. Shoulder screws have three sections: head, shoulder, and thread. The head is the largest diameter section of the shoulder screw, which prevents ...

For example, a #4 screw has a diameter of 4/32 inches or about 3.2 millimeters. The length is measured from the bottom of the head to the tip of the screw. But why do screws come in different sizes?