Ask the Fastener Distributor | What Is a Set Screw Used For?

Widely used in all types of industries, the set screw is most often installed to secure two objects together without the need to drive completely through one the objects. For example, a gear is usually secured to a shaft using a set screw. Your fastener distributor will carry a selection of set screws to suit […]

Widely used in all types of industries, the set screw is most often installed to secure two objects together without the need to drive completely through one the objects. For example, a gear is usually secured to a shaft using a set screw. Your fastener distributor will carry a selection of set screws to suit any application, although an understanding of the design process may help you to choose the optimum type.

How Is a Set Screw Designed?

Most types of set screws have been designed without a head, meaning the fastener is basically one long threaded shaft. This allows the two objects to be fitted snugly together with minimal interference.

Holes in the objects must be threaded to match the set screw, and drilled to the proper depth if a snug fit is required. You need an internal wrench to install or remove set screws, as the socket head is embedded into the ends for an easy fit. Some types of set screws can be tightened and loosened with Allen keys or hex keys, depending on the shape of the internal head.

Points on a set screw vary, depending on the type of application and specific requirements. You'll find set screws with a flat or blunt point, where both objects must be pre-drilled before installation. This design allows for a very snug fit on the ends. You can also order set screws with cone points, or extended points (sometimes called dog points). Looked for dome points, which are well suited to more specific applications and materials, and cup points, by far the most popular on the market today.

Cup tips or points maintain a secure grip without giving way to wear, while the knurled cop design has some locking action to prevent against vibration. As a general rule, set screws are only used in light loads and are not designed for extreme conditions.

Drive styles found on set screws include the popular hex and square sockets, as well as the traditional straight slot. Straight slot set screws have been used for years, with the others only coming onto the market at the beginning of the 20th century.

When your application calls for two objects to be secured together with a firm fit, ask your fastener distributor whether a set screw will do the job. These handy fasteners have been in use for centuries and provide reliable performance in many products, machinery and structures.