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. 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. Land Roverand other smaller,specialised car makersused a mixture of imperial fittings into the 1990's. Both Whitworth and British Standard Fine were phased out by the 1960s,but some manufacturers carried on usingboth on applications much later than this.

bolts and the tools to work on them as British (mainly BSW and BSF)and US (UNF and UNC) machinery used completely different systems. By about1965 BSW and BSF were considered obsolete although theymay still be found in later,specialised applications. This is not strictly correct,although some will loosely 'fit' the thread angle on Unified threads is 60 degrees against the55 of Whitworth. I'm sure hot water cylinders have moved on, but sparkeys still get to work on stuff that's straight out of the ark. These may have greater tolerance than 12 sided sockets but there is always a risk of damage to socket and or the fastening.

Coarse threads (whitworth,unc etc) are more likely to be used on the thread in a casting(especially aluminium) to give greater strength,most nut and bolt assemblies will use a fine thread,so studs in castings often have a coarse thread end to go in the casting and a fine end to take a nut. 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. 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. I Needed a 52 mm socket the other day and had loaned mine out (typical) but it is coming back 60 odd miles! 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.

Sidchrome, Kincrome, TTI, and Milwaukee’s sockets are designed for durability, strength, and use in the most demanding environments. S.F (British Standard Fine) spanner refers to thediameter in inches of the threaded portion on the bolt it fits.S.W) takes its name from the British engineer who invented it as a way of standardising bolt and nut sizes. inch is not a commonly encounteredWhitworth size,13/16 inch and 15/16 inch are even less so and were very seldom specified on engineering drawings etc.

Before about 1948 BSW and BSFnuts and bolts(needing BSW/BSF tools) were commonly used on cars,motorcycles and machines especially those made in the U.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. 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. This was another standard introdued to try and rationalise the sizes of smaller fixings,and which now confuses greatly the metric spanner wielding enthusiast.

I needed a 75mm a little while ago 'in the field' and could not get back for my socket, the wheel brg had gone so found a 75 mm hex pipe fitting and ground it down slightly got some 30x 6mm heated it and folded it round the hex of the pipe fitting, to form the hex required then welded that to the end of a strip of 14mm thick flat plate, shoved the trucks hyab against the plate to hold it onto the hub and hit the end of the plate with sledge, to undo it, again worked a treat. I did similar with a 2ltr montego rally chase car stuck in monaco, when they were new, wired the injectors to the coils with bulbs as resistors coz the ecu went T/U ( turned out it actually was the accident g switch wiring into ecu btw) and would take a week to get the new one out to it. There are two 'standards' of Whitworth/BSF sizes (see foot of page) but the same spannerscan be used oneither . It is very common to find an older car or bikethat left its maker witha mixture of imperial and metric nuts and bolts holding it together.Measuring your lock nut ensures you're using the correct socket and tools, making mounting and dismounting hassle-free.