Inch Hex-Socket Shoulder Screws (ASME B18.3) are specified where the joint requires locating moving parts on a defined shoulder with a hex-socket head. The sections below cover the typical end-uses by industry, the size and material decisions for each, assembly practice, and the applications this fastener type is not suited to. Stocked across roughly 12 to 34, they cover heavy and structural work.
Typical Applications for Inch Hex-Socket Shoulder Screws
The most common settings where these are specified:
- Robotic linkages: socket-head shoulder screws used as repeatable pivots.
- Die and mold tooling: guide points where the cylindrical shoulder is held to size.
- Test fixtures: replaceable stops and locating posts in compact assemblies.
- Machine guards: recessed shoulder hardware installed with a socket driver.
How to Specify Inch Hex-Socket Shoulder Screws for Your Application
- Size: Match the nominal size to the mating thread or hole. This product spans 12–34; check the full table below for the exact dimensions of each size.
- Strength class: Choose the property class (e.g. 8.8, 10.9, 12.9 or A2/A4 stainless) for the load and environment, and tighten to the matching torque so the joint relies on preload, not friction.
- Environment: For damp, coastal or chemical exposure prefer A4/316 stainless or a suitable coating; indoors, plated steel or A2 is usually sufficient.
- Standard: This product is supplied to ASME B18.3. Quoting the standard on your order guarantees interchangeable dimensions between suppliers.
Installation & Assembly Practice
- Tighten to the torque for the size and property class with a calibrated wrench — the joint is held by preload, not by the thread friction alone.
- Ensure at least one full thread projects beyond the nut after tightening, and never re-use a bolt that has been tightened into yield.
- Under slotted or oversized holes, fit a hardened washer so the preload does not relax into the hole edge.
Common Selection Mistakes with Inch Hex-Socket Shoulder Screws
- Specifying class 12.9 "to be safe" in a corrosive environment — high classes are more sensitive to hydrogen embrittlement and stress corrosion; 8.8 hot-dip galvanized often outlasts them outdoors.
- Choosing a length that puts the shear plane through the threaded portion when a plain shank (partially threaded bolt) was available.
- Mixing stainless bolts with plated-steel nuts: the joint loses its corrosion logic and can gall or seize.
Where Inch Hex-Socket Shoulder Screws Are Not the Right Choice
Not for permanent joints that will never be opened (a rivet or weld is cheaper), and not where the head must sit flush — use a countersunk screw instead.
