Hobson BSW Flat Head Socket Screw, 1/4" / 2"

The Hobson BSW flat head socket screw has a BSW (British Standard Whitworth) thread and is alloy steel, plain finish. There are 13 items: 1/4" to 5/8", in lengths from 3/4" to 3-1/2". Head style: FHCS, Flat Head (Countersunk) Cap Screw.

The head is tapered so that it sits flush in a countersunk hole. BSW means British Thread Standard Whitworth and TPI means threads per inch. It changes with the size and length.

Where this product is used

• Fixture and tooling plates where the work face has to stay flat
• Machine covers and wear plates where a raised head would foul a moving part
• Replacing flat head (countersunk) socket screws of the same thread form, diameter and length
• Workshop jobs where the part is protected by its surroundings
• Choosing between the 13 items here: they cover diameters from 1/4" to 5/8" and lengths from 3/4" to 3-1/2"

Features

• 13 items: 1/4" to 5/8"
• BSW thread, flat head socket screw
• Alloy steel
• Plain finish
• Pack quantity shown for each item
• Plain (uncoated) steel for dry indoor and machinery use
• Material: 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.

Plain (uncoated) steel has no corrosion protection beyond a light oil film, and it rusts quickly once moisture reaches it. 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.

BSW is the Whitworth thread, a 55 degree imperial form found on older British-origin equipment. Match it with BSW nuts and tapped holes. 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 Flat Head Socket Screw, Alloy Steel, Plain, #10-24 to 1", Hobson UNF Countersunk Hex Socket Screw, Plain, 1/4" to 1/2" and Hobson UNC Flat Head Socket Screw, Zinc, 3/8 x 1", Box of 100.