Heat Treated Alloy Steel Socket Head Cap Screws (also known as Allen head screws) have a cylindrically shaped head with a flat top, knurled cylindrical sides and an internal hexagonal drive recess, often called an Allen or Hex drive. With a minimum tensile strength of 170 ksi they are stronger than Grade 8 bolts. Their high strength and compact head design making them ideal for use in tight or confined spaces and they are often seen on Industrial machinery. The internal hex (Allen) drive also eases their use in tight spaces by allowing easier access for the user to apply sufficient tightening force on the fastener during installation.

These fasteners are commonly used in applications where it is necessary to recess (counterbore) the head of the fastener, or in confined spaces that limit the size of the fastener head or that restrict access for the tool that drives the fastener. Socket head cap screws made from high strength alloy steel meet the material requirements of ASTM A574 and have a minimum tensile strength ranging from 180 ksi to 170 ksi depending on fastener diameter. They feature a Black Oxide finish for moderate corrosion resistance in dry environments. The Black Oxide finish also lubricates the fastener threads, reducing installation torque and effort. Thread lengths listed on this site are the minimum industry standard thread lengths. The actual thread lengths received may be longer than what is shown here. Socket Head Cap Screw length is measured from under the head, not overall length.