Socket Head Cap Screws

Socket hex head cap screws are machine screws that have external threading and are designed to be driven with an internal hex socket drive, which matches a hex key or allen wrench. These screws have the advantage of requiring less surface area because they can be wrenched internally, making them a great choice for projects with limited space that cannot accommodate traditional wrenches or sockets

Socket head screws, also called Allen screws or Allen head bolts, can be either fully or partially threaded. On fully threaded screws, the thread length equals the screw length, and the screw can be installed all the way into a threaded hole. Conversely, partially threaded screws have an unthreaded portion under the head and therefore, the thread length varies. Because the unthreaded portion of the screw is stronger than the threaded section, partially threaded screws possess more holding power when force is applied from the side.

AFT's cap screws are available in metric and inch sizes in a wide range of diameters and lengths.

Nylon Patch or Nylon Pellet

Nylon patch socket head cap screws are screws that have a nylon patch applied to the threads of the screw. The nylon patch serves as a locking mechanism to prevent the screw from loosening over time due to vibration or other factors. When the screw is tightened, the nylon patch is compressed against the mating threads, creating a frictional force that resists loosening.


Socket head cap screws are typically manufactured using either alloy steel or stainless steel. However, there are also other options available such as silicon bronze and Ni-Cu Alloy Steel.

Should you not find the style or finish that you desire on our website, please let us know. With on-site plating and coating facilities, we are able to customize any fastener with your desired modifications, including painting, plating, drilled holes and custom lengths.

Socket Head Cap Screw Resources

Frequently asked Questions

Q: What grade are socket head cap screws?

A: Standard inch socket head cap screws are not designated by a grade like hex cap screws. A standard inch socket head cap screw is 20% stronger than Grade 8 hex cap screws and 50% stronger than Grade 5 hex cap screws. Metric socket head cap screws are designated by classes - Class 8.8, Class 10.9 & Class 12.9.

Q: What is the typical finish for socket head cap screws?

A: One of the most common finishes for socket head cap screws is black oxide. This finish provides corrosion resistance and a sleek, black appearance. Other common finishes for socket head cap screws include zinc plating, which also provides corrosion resistance, and plain finish, which is untreated and has no protective coating. The choice of finish often depends on the specific application and the level of corrosion resistance required.

Q: Do socket head cap screws need washers?

A: Washers aren't commonly required when using socket head cap screws. Exceptions may include applications with soft materials or irregular surfaces. If a washer is needed, try using a hi-collar split lock washer.