Shoulder Screws

Also known as stripper bolts and shoulder screws, shoulder bolts are available in a variety of styles to suit the huge range of mechanical applications in which they're used. Made in both standard and precision grades, these versatile fasteners are machined to high tolerances. Even though the threaded section of the bolt is short in comparison to the shoulder, the thread pitch is designed to provide maximum thread engagement with the workpiece for strong and reliable fixing.

Used to create pivot points and bearings, a shoulder bolt can be used in conjunction with a washer and bolt to allow for movement. Alternatively, a nylon lock nut will also do the job. Designed to use mainly hex socket and slot drives, users can utilise a general-purpose screwdriver set when working with shoulder bolts or invest in a Torx driver set.

Here at Cromwell, we supply shoulder bolts from our own quality brand Qualfast®.

What are shoulder bolts?

Shoulder bolts feature a section between the head and the threaded tip called the shoulder. This section is unthreaded and designed to ensure a component can rotate or slide when required. Some shoulder bolts need slotted drivers, but most require a hex key to fasten them.

Why shoulder bolts?

A cost-effective fastener, shoulder bolts are precision engineered to provide a reliable fit. They're used in a range of industries where safe fastening is paramount, and their design makes them useful to use in compact spaces.

When are shoulder bolts used?

Shoulder bolts are used in a variety of industries, including aerospace, vehicle repair, machine tooling and production.

Shoulder bolt types

There are six basic types of shoulder bolts to suit most tasks. Mainly engineered using steel, these cost-effective fasteners sometimes feature surface treatments on the head and screw tip to ensure longevity.

• Socket shoulder bolts   -   Require a socket drive or hex socket key

• Low head socket shoulder bolts   -   Feature a large shoulder and reduced head depth

• Slotted pan head shoulder bolts   -   Feature a flat, shallow head with a slotted head

• Knurled socket shoulder bolts   -   Designed to fasten mainly by hand with a knurled head

• Precision slotted shoulder bolts   -   Machined to a high tolerance with a slotted head

• Headless slotted shoulder bolts   -   The slotted driver is machined into the shoulder with no head

Considerations when choosing a shoulder bolt

• Fitting - Mainly available in slotted and hex socket drives.

• Thread size - Sizing ranges between M4-M12.

• Bolt length - Choose to suit the length of the workpiece.

• Shoulder dimensions - Once installed the shoulder will sit above the surface to provide the action required by the user (dowel, guide, pivot etc). The dimensions of the shoulder should suit the application.

• Material - Mainly made of steel and stainless steel in its various forms.

• Finish - Often supplied in plain finishes, sometimes the head and threaded section are treated to ensure strength and durability.

• Thread pitch - Should be deep enough to ensure good thread to material contact for a strong hold.

Shoulder bolt jargon buster

We want to make it easy to browse our selection of shoulder bolts, so here are some key terms that will help to explain the range and applications a little better.

What does the standard ISO 7379:1983 mean?

ISO 7379:1983 is not as complicated to understand as it first appears. It outlines the technical specifications and tolerances expected for hexagon socket head shoulder screws with shoulder diameters of 6.5mm-25mm.

Let's break it down...

• ISO - This standard was produced and published by the International Standards Organisation

• 7379 - This is the assigned legislation number

• 1983 - This is the year that this standard was published. Standards are reviewed every five years, and this one was checked and confirmed in 2020.


Do shoulder screws need washers?

This depends on the application and how much pressure the bolt will be under. For moving parts, a washer usually sits under the bolt head.

How do I identify a shoulder screw?

Shoulder screws can be identified using the shoulder length and thread pitch. For example, M8 x 25mm Steel shoulder screw.