Collezione: Socket Screw, Cap Head

Socket Screw/ Allen Bolt, Cap Cylindrical Head

‘Socket,’ is characterised by hexagon shaped indentation found on the top of the fasteners’ head. Here, you can use a hexagon key (or allen key) to tighten and loosen the fastener.

 A socket screw can come as a screw or bolt. A bolt is term is used to describe a fastener that is partially threaded with a part plain, un threaded shank under the head. A bolt is most commonly used through a clearance hole and fastened with a nut and washer to secure components together. A screw is fully threaded and most commonly used to turn into a pre threaded component. 

Allen socket, Cap Head Screw/ Bolt Applications

An allen socket, cap head screw is best used in engineering applications where you are joining components under heat and or high compression, tension, torque or shearing stress. For example, fastening together automotive or machinery parts. Allen socket, cap head screw/ bolts are designed to be used as a temporary fastener where components need maintenance or should be replaced due to functional wear.


They are available in the following materials (please note; not every head type is available in every material):

Material/ Finish


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/ Oilied

High Tensile Steel - Zinc

Bright Shine – Blue to Yellow


-          Low exposure to moisture

A2 Stainless Steel

Dull Shine


-          Intermittent weathering

-          Hygiene

A4 Stainless Steel

Dull Shine


-          Constant Weathering

-          Chemical exposure


Off white


-          provide electrical insulation.

-          Low weight

-          Minimal load



Metric Coarse and Metric Fine

Are in Millimetre (mm) units and were developed to simplify the imperial systems. Europe moved to this system but the Americans choose Imperial as their default. A coarse thread has less helical coils per mm and a fine one has more. Coarse is used for heavier loads and fine is used for lighter loads prone to vibrations.


British Association (BA)

screw threads, named after the British Association for Advancement of Science, were devised in 1884 and standardised in 1903. Screws were described as "2BA", "4BA" etc., BA threads are specified by British Standard BS 93:1951 "Specification for British Association (B.A.) screw threads with tolerances for sizes 0 B.A. to 16 B.A." They are associated with metric units of measurement.


British Standards Brass (BSB)

Is a specialist thread form based upon the Whitworth thread and consisting of 26 threads per inch (imperial) whatever the thread diameter.

British Standard Cycle Thread (BSC)       

BSC Thread has extra fine threads 26 TPI originally for use on bicycles and motorcycles. The thread runs at a 60 degree rather than a 55 degree angle.

British Standard Fine (BSF)       

A thread form based upon the British Standard Whitworth form but with a finer thread; more threads per inch and has the same thread angle as the BSW and smaller thread depth.

BSF was developed by R E B Crompton and his assistant George Field and was first introduced in 1908, the thread form is specified in BS 84: 1956

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



The basic American standards for fastening screw threads as agreed upon by standard bodies of Canada, the United Kingdom, and the United States. They are a complete and integrated system of threads for fastening purposes. Their outstanding characteristic is general interchangeability of threads achieved through the standardization of thread form, diameter-pitch combinations, and limits of size


Unified National Coarse (UNC)     

is a thread form with a 60 degree flank angle rounded roots and flat crests. For a given diameter it has a larger thread pitch than an equivalent diameter UNF thread. The unified thread is based on inch sizes and was first standardised in 1948 unifying the Whitworth and American standard thread forms

Unified National Extra Fine (UNEF) 

is a Unified thread form with a very fine (small) pitch that are typically used on instruments and parts requiring a fine adjustment.

Unified National Fine (UNF)

is a thread form with a 60 degree flank angle rounded roots and flat crests. For a given diameter it has a smaller thread pitch than an equivalent diameter UNC thread.

Unified National (UN)

thread form with a rounded root contour, applies only to external threads. (The UN thread form has a flat, or optionally, a rounded root contour.) The majority of fasteners with a Unified thread form (UNC UNF) have a rounded root contour i.e. are UNR threads.