Hobson UNC Socket Head Cap Screw, 4-40 / 3/8"

The Hobson UNC socket head cap screw has a UNC (Unified National Coarse) thread and is alloy steel, plain finish. There are 140 items: #4-40 to 1-1/2", in lengths from 1/4" to 12". Head style: SHCS, Socket Head Cap Screw.

The head carries a socket, so the screw is driven with a key or bit instead of a spanner. UNC means Unified National Coarse Thread and TPI means threads per inch.

Where this product is used

• Jigs, fixtures and die sets that are assembled and re-set with a hex key
• Motor, pump and gearbox mounting where the head is recessed below the surface
• Replacing socket cap screws of the same thread form, diameter and length on machinery
• Workshop jobs where the part is protected by its surroundings

Features

• 140 items: #4-40 to 1-1/2"
• UNC thread, socket head cap screw
• Alloy steel
• Plain finish
• Pack quantity shown for each item
• Plain (uncoated) steel for dry indoor and machinery use
• Made from alloy steel

Key specifications

Choosing the right option

Choose the thread form first: the screw must match its nut or tapped hole in thread form, diameter and pitch.

A plain finish means bare steel with only a light oil film on it. It will rust quickly in damp conditions. That makes it a good fit for dry indoor work, machinery, and assemblies that are painted, oiled or enclosed after fitting. For anything outdoors or damp, choose a hot dip galvanised or 316 stainless option instead. In tooling and machine building, plain alloy socket screws are the usual choice, where the assemblies are usually oiled or enclosed.

The thread is UNC (Unified National Coarse), the general-purpose inch thread. Use it with UNC nuts and tapped holes only. For load-critical, structural or lifting joints, confirm the fastener against the engineer's specification. Fasteners are not lifting rated unless marked.

Related socket screws: Hobson UNC Socket Head Cap Screw, Alloy Steel, Zinc, 1/4" to 5/8", Hobson UNF Socket Head Cap Screw, Alloy Steel, Plain, #10-32 to 1" and Hobson UNC Button Head Socket Screw, Alloy Steel, Plain, #10-24 to 1/2".