What are shoulder bolts?
Shoulder bolts—also called stripper bolts or shoulder screws—have a precision, unthreaded shank (the “shoulder”) and a smaller threaded tip. The shoulder acts as a smooth, accurately sized axle or bearing surface for parts that need to pivot, slide, or locate with tight repeatability.
Why choose shoulder bolts
- Precision location — close-tolerance shoulders position parts and tooling accurately.
- Smooth motion — the polished shoulder provides a low-friction bearing surface for rotating or sliding components.
- Serviceable design — the threaded tip allows straightforward assembly and removal for maintenance.
- Versatile heads & drives — common options include socket head (most precise/compact) and hex head where wrench clearance is needed.
Materials & finishes for shoulder bolts
- Alloy steel (black oxide) — high strength and good wear; common for tooling and fixtures.
- Stainless steel (18-8 / 304) — broad corrosion resistance for general environments.
- Stainless steel (316) — enhanced resistance for coastal/chloride exposure.
- Zinc-plated steel — economical corrosion protection for light industrial use.
Common applications for shoulder bolts
- Tooling and fixtures, die sets, and stripper plates
- Hinges, cams, linkages, and pulley/idler mounts
- Automation & robotics guides and end-effectors
- Sliding mechanisms in jigs, conveyors, and machine guards
- Precision locators for assemblies and test equipment
How to size and specify shoulder bolts
Order by shoulder diameter × shoulder length × thread size (e.g., 1/2″ × 1-1/2″ × 3/8-16). The shoulder length is measured from under the head to the start of the threads, and should be long enough to carry the moving parts without riding on the threads. Match fit (clearance vs. close) to your mating hole, and select the head style/drive to suit your tool access.
Installation tips for shoulder bolts
- Clamp on the threaded portion, not the shoulder, when free motion is required.
- Use washers or spacers so parts bear on the shoulder and not the head or threads.
- Apply appropriate torque to the threads; use threadlocker or a prevailing-torque nut if vibration is present.
- For close-fit applications, ream the mating hole to the specified diameter tolerance.