UNC and Whitworth have the same thread rates but the thread form is different,a thread gauge would help to make accurate comparisons. The Laser 1583 18mm 1/2" Drive Spark Plug Socket is perfect for working on unusually sized spark plugs that are becoming more common and a variety of motorcycles. B.A (British Association) are smaller sized fastenings found on older vehicles electrical fittings,magnetos,dynamos,motors,pumps and instruments etc.

The Laser 4376 14mm 3/8" Drive Thin Wall Spark Plug Socket has been especially designed to be used on most Citroen vehicles as well as vehicles with Bosch spark plugs, such as the BMW E90335I N54 engine. This standard was introduced asthe 'new' standard around the 1940sto replace BSW and BSF etc and was supposedly phased outby the 1970's in favour of metric threads and sizes. I Needed a 52 mm socket the other day and had loaned mine out (typical) but it is coming back 60 odd miles! Imperial AF spanners are normally used on nuts and bolts threaded UNC or UNF (Unified Coarse or Unified Fine) and use a thread angle of 60 degrees. S.F and MMbolt or nutsand can be used for example to find the next size up or down where a spanner (wrench in USA)or socket is too tight or loose on a fixing.

These may have greater tolerance than 12 sided sockets but there is always a risk of damage to socket and or the fastening. If youknow if the thread is fine or coarse and when the item was made it will help work out what size the original fitting is.

Long time ago, My xk150 SU petrol pump packed in, A couple of new replacements didn't last more than a few weeks, Used to keep on the move when they stopped working by leaning out of the drivers door, reaching under the sill and giving the pump a good smacking with my hand, And that would get me another half mile or so, When they wouldn't change the faulty pumps anymore.this occurs throught the sizes so a set of whitworth sockets or spanners will fit an equal number of BSF nuts and bolts. S.W) takes its name from the British engineer who invented it as a way of standardising bolt and nut sizes.

The Draper 16706 is a 12 point socket manufactured from chrome vanadium steel that has been hardened and tempered for reliability and is completed with a polished finish. All the commonly used spanner and socket sizes,from10BA up to 60mm with their decimal inch equivalents. Damaged bolt heads spoil the restoration or repair of many a rebuilt classic car or motorcycle,theres no need when the correct spanners are still available . A whitworth spanner or socket is larger thanone marked with the same size in BSFfor example a1/4 inch whit is thesame physical size as a 5/16inch BSF.

A tubular box spanner or six sided socket thenext size up might be a solution when the correct size is not available (ie) a 19mm spanner will probably undo a 3/4 inchaf nut. Usually applied to spanners in imerial (inch based) sizes the smallest increments are normally 1/16inch (for example 7/16,1/2,9/16 etc) but some smaller spanners are marked in 1/32 inch increments. You can use a vernier caliper to measure the internal and external diameter of the nut or use a tape measure to measure its bore size. You can use the abovechart (and the AF/metric chart below) to find equivalents for some missing tools. It also shows when some spanners and sockets are almost the same physical size although displaying different markings for example 11/32 inch AF and 1/8 inch whitworth are identical.

By the end of the 1970s UNF and UNC hadalmost gonethe same way,replaced by the metric although they too can still be encountered inpost 1970'smachinery. This versatile device is suitable for use with bearings mounted on an adapter or withdrawal sleeve, as well as on a tapered journal. There are two 'standards' of Whitworth/BSF sizes (see foot of page) but the same spannerscan be used oneither . A.F means Across Flats and indicates the distance apart the jaws are on an open end wrench (or the parallel sides on a nut or bolt.

Sidchrome, Kincrome, TTI, and Milwaukee’s sockets are designed for durability, strength, and use in the most demanding environments. Duologi is the trading name of Specialist Lending Ltd, which is authorised and regulated by the Financial Conduct Authority (register number 774712).