Learn the common sense of threaded fasteners



This article will visually introduce some of the different types of screws and bolts, focusing on different screw heads, driver types and bearing faces. The "bearing surface", also known as the underside of the screw head, is where the fastener head makes contact with the device. To improve tensile strength; Some bolts and screws have shoulders set under the head.

Below is an introduction to the different types of threaded fasteners.

Bolt : is a fastener that is threaded through a hole with a cylinder with external threads and fixed to a specific torque specification with the help of a nut. The most common type of head is hexagonal. Other head types include spade, square, carriage, T-shaped, U-shaped, hanging ring, etc. Depending on the application, thread types can be divided into coarse (UNC) or fine (UNF).


Caped screws: Similar to bolts, but with tighter tolerances. These screws also have external threads that can be fastened to the mating object. The hexagonal type is also known as "hex delicate bolt".

Machine screws: typically used in precision applications. It can be paired with both nuts and threaded holes on the device. The thread diameter on the rod is uniform. They need to be fixed to the device (such as cross, flat, hex, etc.) with a drill bit placed on the head, and the role of the drill is to embed it in the device by rotating the screw head. Thread sizes are available in fine and standard sizes. The thread can be cold-rolled by precision mold or processed into a rod.


Panel screws: Both threadless and threaded sections under the head. The threadless section allows the screws to be freely attached to the device panel.

Sheet metal screw: is a self-tapping or self-threading fastener with a non-uniform thread.

Shoulder screw: A fastener with an unthreaded part on a rod under the head. This smooth section makes it easy to use with bearings, axles, grommets, etc.

Airfoil screw: A screw that the head can be turned with thumbs and fingers.
Set screw: A screw that is fully threaded and has no head and can be fixed to or inside another object.