Different types of internal polygon screws/bolts

Type 1: Square head screws

The primary advantage to Square head screws is they are much less prone to “cam-out.” Cam-out refers to the slipping of the bit in the screw head as the screw is driven. The square-head screw was invented by P. I. Robertson, a Canadian, in 1908.

Type 2:Security hex screws

Security hex screws are designed to stop theft and vandalism. A security screw makes it more difficult for the vandal or criminal to get access to their target. ... Tanner is a leading distributor of security screws.

Type 3:Roberston screws

After badly cutting his hand while using a slot-headed screwdriver, Peter Lymburner Robertson invented the square-headed screwdriver and screw in 1908. He received the Canadian patent for his invention in 1909.

Type 4：Double-square screws

Type 5:Hex screws/bolts

A hex “tap” bolt is a term used to describe a fully threaded hex bolt. Many of our customers will use the terms “Hex Tap Bolt” and “Fully Threaded Hex Cap Screw” interchangeably. Remember, that in the U.S., a “bolt” is a fastener that is designed to be used with a nut.

Type 6:Hex socket set screws/allen head screws/cap head screws

In 1919, Dyke defined them as screws that are threaded all the way to the head. A socket cap screw, also known as a socket head capscrew, socket screw, or Allen bolt, is a type of cap screw with a cylindrical head and hexagonal drive hole.