I'm probably guilty of having taken the standardisation of nuts and bolt for granted. Things are likely to be Metric, and because I often work on older items then Imperial. Then occasionally neither are quite right ... and thats where Whitworth (BSW) comes in (sometimes.)
British Standard Whitworth (BSW) was the worlds first screw thread standard. Set in 1841 by Joseph Whitworth. Prior to this individual manufactures or industries used their own fasteners. If you'd like to know more I highly recommend reading "Exactly" by Simon Winchester.
One thing to remember is that Whitworth spanners are sized by the bolt diameter, not the distance across the hex head sides as with Metric and Imperial. What that means is a 1/2 BSW is massive when compared with 1/2 BSF.
So do you need a set of Whitworths? Probably only if you regularly work on pre-WW2 vehicles or machinery. Anything in that 100 years up to 1940 might well be Whitworth. But the parts bins at British automotive manufactures were large and tail of the odd Whitworth fastening use was quiet long. At a show recently we learned that E-type Jags up to the early 1960's still used them a lot.
If you work on classic British cars up to the 1970's then there is one place were you are very likely to need a Whitworth spanner. Have you wondered why the nut on your battery terminals seems to be between 1/2 BSF and 13mm? That's because it's likely to be 1/4 BSW!
Apparently the standard tripod mount for SLR cameras is still 1/4 BSW as well.
King Dick are one of the few manufacturers in the world still making Whitworth.
Hot forged from 31 CrV3 Chrome Vanadium Steel Precisely machined, heat-treated and nickel-chrome plated
Made to DIN 3113
The 1/4 x 5/15 Heritage Black is a modern take on the traditional black finish on spanners and tools.
We also stock Imperial and Metric combination spanners from King Dick.