What is the difference between a hex bolt and an Allen bolt?

A hex bolt and an Allen bolt are similar in function but differ in their design and the tools used to tighten or loosen them.

Hex Bolt: A hex bolt, also known as a hex cap screw, has a head with six flat sides and is typically tightened or loosened using a wrench or a socket. The head of a hex bolt is usually larger and may protrude from the surface it's attached to.

Allen Bolt: An Allen bolt, also known as a socket head cap screw, has a cylindrical head with a hexagonal socket (recess) in the center. It requires an Allen key (also known as a hex key) to tighten or loosen it. The head of an Allen bolt is typically smaller and sits flush with the surface it's attached to, which can be advantageous in certain applications where space is limited.

So, while both bolts have a hexagonal shape, the main difference lies in the method of tightening or loosening them and their respective head designs.