Brake bleeding

REALLY?

Care to call again once you know WTF you are talking about?

I think you may find that BS actually stands for British Standards.

See........

And I think you may find that it is equal to the bolt size, ie a spanner marked 1/2" B.S will fit the British standard head of a 1/2" bolt.

For instance, one of the longest remaining common applications was the use of a 1/4"W spanner for battery terminals. The spanner would be marked1/4"Whit/ 5/16" B.S, and it would fit the 5/16" bolt through the battery terminal.

Steve

During the war...

Chris

But it wont fit a 1/2 inch UNC bolt, or a 1/2 inch whitworth bolt, even though the 'bolt size' on both those is 1/2 inch.

And up to the seventies, according to this guy.

And it continues. The 1985 Ford Cargo I owned until recently had ISO metric fasteners for the chassis and cab, but (mostly) UNF/UNC on the major assemblies.

Steve

True, but then the Americans never bother themselves overmuch with Brit conventions.

or a 1/2 inch whitworth bolt, even

Actually it will fit a 1/2" (stem) bolt with a whitworth thread, which will have a 7/16"W hex head. The spanner will be marked 7/16"W/1/2"BS This is not correctly a 1/2" W bolt of course, but it all adds to the fun.

But we've drifted from my point now which was to point out the potential confusion caused by the dual markings. I was using = to signify "is equal to" rather than "stands for"

Steve

But that's the whole point, it isn't equal to the 'bolt size', unless it is a British standard bolt. Hence the mark 'BS' to indicate that they are referring to British standard bolts. The confusion only arises if people don't understand what the markings mean, which is why I pointed it out.