A set screw is the type of screw used if a nut is not needed or cannot be incorporated in the application. It’s also called a blind screw or a grub screw. Set screws are mainly used when one needs to secure an object against another object or within another object, for example, a pulley to a shaft or a potentiometer knob. The set screw locks it in place. Set screws are driven into a threaded hole in the outer object and then tightened against the inner one.

What sets set screws apart from the other screws is that they’re fully threaded. However, there are types such as the Square Head Set Screw that has an unthreaded head. Square head set screw can be cone point, cup point, flat square, half dog square, or oval point square. Cone point has a cone shaped head and the tip has a sharp point. Cup point has a slightly circular and concave shape. Flat has a flat circle metal. Half dog is half as long as Full Dog. Oval point has a convex circular head.

Set screws are used with a hex socket, torx screws, square socket, or a slot–basically, any internal-wrenching drive.