
BSW-Whitworth, 5/16", Cap Head, Socket Screw.
BSW-Whitworth, 5/16", Cap Head, Bolt/ Socket Screw/ Allen Bolt, High Tensile (12.9), BS 2470.
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A screw is fully threaded, a bolt is partially threaded. Hence, the different name in the title, ‘Socket Screw/ Allen Bolt’. So, generally speaking the fastener is a screw in lengths around 1-2inches/ 25-50mm (depending on diameter: they can vary up to ½ Inch/ 12mm with different diameters). The fastener becomes a bolt when there is space of unthreaded area on the shank, under the head. ‘Socket,’ refers to the hexagon shaped indentation found on the top of the fasteners’ head. Here, you can use a hexagon key (Allen Key) to tighten and loosen the fastener. The length of a fastener is measured from the point at which it fully touches the material to be fastened.
They are available in the following head types:
- Cap Head
- Countersink Head
- Button Head
- Flange Button Head
- Grub
- Shoulder - Cap Head
They are available in the following materials (please note; not every head type is available in every material):
Material/ Finish |
Appearance |
Level of Corrosion Resistance |
Typical Application |
High Tensile Steel |
Self-Colour (black with no surface treatment) |
Low, without further surface treatment |
- No exposure to moisture - Often Greased/ Oiled |
High Tensile Steel - Zinc |
Bright Shine – Blue to Yellow |
Internal |
- Low exposure to moisture |
A2 Stainless Steel |
Dull Shine |
External |
- Intermittent weathering - Hygiene |
A4 Stainless Steel |
Dull Shine |
External |
- Constant Weathering/ Exposure |
Nylon |
Off white |
High |
- Provide electrical insulation. - Low weight - Minimal load |
UNITS OF MEASUREMENT FOR THREAD TYPES
British Standard Whitworth (BSW)
A thread form developed by Sir Joseph Whitworth in 1841. The thread form has rounded roots and crests, a thread angle of 55 degrees, the thread form is specified in BS 84: 1956
Image is for illustrative purposes only.
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