4-1/2", 20

Bolts with hexagonal heads and machine threads for use with a nut or in a tapped hole. Also known as hex cap screws or machine bolts.

Screws with machine threads for use with a nut or in a tapped hole.

Bolts with no drive and machine threads for use with a nut.

Screws with an Allen wrench drive.

Hanger bolts and dowel screws are used for adding an external machine or screw thread to wood applications.

Screws with an unthreaded shoulder that is larger in diameter than the threads. Also known as stripper bolts.