Hex Head Machine Bolt

Hex Head Machine Bolt Description

Hex head machine bolt are used to fasten wood to wood, wood to metal and metal to metal. Similar to a hex cap screw, a machine bolt will differ in these four ways: its point will not be chamfered or rounded; it will be available in larger sizes (diameters); it will not have an underhead washer bearing surface; and it will be manufactured to less exacting standards. Depending on head style, machine bolts are also known as: hex bolts, square bolts. They are used with nuts and internally threaded (tapped) holes.

Threads are standard right-hand and often Unified inch coarse series. Short lengths are fully threaded while longer lengths follow a standard formula: for bolts 6" and shorter, the minimum threaded length is two times the basic thread diameter plus 1/4", and for lengths greater than 6", two times the diameter plus 1/2".

Typically, machine bolt sizes range from 1/4" to 1 1/4" for square heads and 3/8" to 1 3/4" in diameter for hex heads, and lengths span from about 3/4" to 18" for square and 6 1/2" to 24" for hex heads. Measure length from under the head to the threaded end of the bolt.