definitions used throughout this site.
British Standard Whitworth,an
early thread standard. Threads are coarse,angle 55degrees and the pitch is
measured in threads per inch.The size marked on the spanner (half inch
whitworth,nine sixteenths whitworth etc) refers to the diametre of
the shank of the bolt it fits not the head size and is always in fractions
of an inch. For this reason a Whitworth spanner or socket is always larger than
AF ones carrying the same size markings.All Whitworth tools will carry a
marking, a fraction followed by W, WHIT or Whitworth and occassionally
W/BSF . Pretty much obsolete by the 60s but encountered on earlier
cars,motorcycles trucks,trains and machinery.
British Standard Fine,in
effect,a fine version of whitworth. Size again refers to the thread part of the
bolt,not the head. BSF spanners are always marked one size larger than the same
sized BSW spanner so for example a 1/4 inch BSW is the same size as a 5/16 inch
British Association,an early
thread standard used on small nuts and bolts.These fixings are mainly found on
electrical components or instruments etc.Still encountered on some relatively
modern machinery and used in model engineering etc.Unusual in the the larger the
number on a spanner or socket the smaller the tool. Sizes normally encountered
range from 0BA to 10BA although sizes from 11BA to 23BA are included in some
text books and manuals.
Stands for Across Flats and
indicates the gap between an open ended spanners jaws and the distance across
the nut or bolts parallel faces.Normally measured in fractions of an inch (7/16
or 1/2 etc) or Millimetres. If the measurement is an exact inch fraction they
sually simply referred to as 'Imperial' or AF and normally used on
UNC or UNF fixings . They are normally marked with the size in fractional
inches (1/2 AF,1/4 AF etc) or sometimes with the decimal inch equivalent
(50AF or 25AF etc). Some are found marked with a fraction and the letters SAE.
If measured and marked in whole millimetres they are intended for
metric threaded fixings and are simply called metric.
Unified Coarse or Unified
Fine,the thread standard that superseded B.S.W and B.S.F etc. Fast becoming
obsolete but commonly used on many vehicles late 50s to 80s or later . Most UNC
and UNF fittings use AF (Inch based) tools.
Six and twelve
Sockets can be six point (shaped inside as
a hexagon) sometimes called mono hex,most impact sockets are six point and
coloured black.Twelve point (or bi hex) sockets are a double hex configuration.
Flank drive,Hi Torq etc are different designs of sockets claimed to drive
without putting force right on the corners of hexagonal nuts and
Anything the size of which uses inches or
fractions of an inch as its measurement. Thus a 1/2inch af,or a 1/2 inch whit is
an imperial sized spanner or socket a 19mm is not,a whitworth sized spanner in
normally called whitworth
There are various types of sockets made
that are supposed to fit everything from mm to torx and Whitworth.We don't sell
them,we hink the correct tool for a half inch whitworth nut or bolt
is the half inch whitworth spanner (or socket) made specifically for it.
There are a few imperial tools that even we can no longer source,in these cases
when a metric tool is very close in size we can probably supply an