Hex-Bolt

Fixaball sell all Hexagon Head Bolts with Metric and Imperial thread types.

Hexagon Head Bolt

Bolt is the term used for a partially threaded fastener (bolt with shoulder/ part plain shank bolt), with a head; designed to be used with a nut and washer. 

Bolt Thread

The thread length of a shoulder bolt/ plain shank bolt tends to be 2.5 times the diameter of the fastener. Please ask for exact measurements if the shoulder is crucial.

Bolt vs Screw

A screw screws into something, a bolt joins several things together from both sides of materials joined. A screw is fully threaded from underneath the head and a bolt is partially threaded (has a part-plain shank)

Zinc/ BZP Coating

Zinc coats the fastener to add moisture resistance to the steel to slow down the oxidisation (rusting) of the metal. It does not make the steel waterproof.  Zinc is used for inernal application for an aesthetic shine (chrome type finish) or where there is likely to be moisture on the screw e.g. garage. Self-colour (no coating) is ok to use with a light covering of oil/ grease, when the fastener is not on show or its appearance is not important.

Metric Coarse (Standard Thread) dimensions are measured 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 than a Metric Fine Thead. Coarse is used for heavier loads and fine is used for lighter loads prone to vibrations.

 

UNIFIED THREAD STANDARDS 

Thread standards agreed upon by standard bodies of Canada, the United Kingdom, and the United States.  

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.

 

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. to represent their unit of measurement eg. 6BA happens to be 6mm diameter (metric equivalent). 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." 

 

British Standard Threads are very rare and hard to source, hence, some of them are very expensive to replenish stocks.

British Standard Fine (BSF) thread form is 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.

British Standard Whitworth (BSW) is 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.

 

International Equivalent Standards

  • ISO 4014
  • CSN 21101
  • PN 82101
  • UNI 5737
  • EU 24014