Mystery socket sizes?
 

I picked up a set of 1/2 drive sockets yesterday, vintage and i cleaned them up and sorted them for my mechanic displays.
So I'm sorting these and can't understand the sizes. Made in USA so I didn't write them off as some eccentric (but perfectly logical, no offence) British thing
As marked and then measured and tried on various nuts and bolts.
marked 1 1/16 = 1 5/16
1 5/8 = 1 1/4
9/16 = 1"
1/2 = 15/16
5/16 = 5/8
3/16 = 15/32
1/4 = 17/32

Any explanation?

British Standard Whitworth ! I have some large 3/4" drive sockets from wartime period, made in USA, think they are Snap-on

Thank you Peter
 

So, woulkd they be of any use to any particular vehicle? Free to a good home. Centurian?

Hi Harry,
I guess a Centurion was made with BSF/BSW threads, as it dates from the 1940's and most British vehicles were using those threads into the 50's and 60's.

regards, Richard

As I understand it the British marked their spanner/socket sizes based on the shank/thread diameter of the bolt, not the distance across the flats (A/F)
I believe that the distance across the flats was arrived at by applying a ratio to the bolt/shank/thread diameter which usually ended up being an odd sort of in between measurement for the distance across the flats.
The Americans went the simpler route and rounded head size to the nearest 1/16"( mostly) and marked their tooling accordingly.

David

Hi David,
I think that was correct pre-WW2, but to save metal the hex head and nut was reduced, so a 1/4" BSF or BS Whit bolt needs a 3/16" Whit spanner, 5/16" bolt needs a 1/4" Whit spanner and so one.

To go slightly off course, I get truck drivers coming into my workshop asking if I have a 10mm bolt, when I question them, it turns out they want a 6mm bolt, they go by the spanner size. Same used to happen with Unified and BS.

regards, Richard

I would think US made BS tools would have a niche but desiring following. Just as there are those who collect British made US pattern field gear and US made British Lend-lease uniform bits.

Matt