What Is a Cap Screw?

A cap screw is a threaded fastener that can be directly tightened into a tapped hole and does not require the use of a nut. They are available with a variety of head designs including hex, socket head cap screws and button head caps. These are used in applications that do not have enough clearance for a wrench or socket.

The basic structure of a cap screw is made from metal and then threads are added. The threads are either cut or rolled into the screw. Cutting involves removing material to create the thread while rolling presses the threads into the screw without removing any material. After the threads are formed the screw is then heat treated to improve its strength.

The type of cap screw chosen for a specific application depends primarily on the force needed to secure a mechanical connection. The screw should be carefully inspected to ensure correct installation and to prevent damage or loosening over time. It should also be properly cleaned and lubricated to minimize friction, which can result in damage or loosening. Lastly, cap screws should be replaced promptly when signs of wear or corrosion appear.