jchamberlin
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- Jul 19, 2010
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- Jeremiah Chamberlin
I was going through the tools collected over the years by my daughter-in-law's father, who was a welder, now deceased. My daughter-in-law tells me he collected EVERYTHING. One of the items was a 1/2" drive socket labeled 31/32" from New Britain.
It seems that this socket was made to fit a 9/16" "Heavy" Hex Nut or Bolt according to the US Standard which was current BEFORE World War II. During the war, what with the US trying to source parts for Britain as well as trying to use parts from them for assembly there was quite a bit of standardization which was formalized in 1949 or so. So that the Unified National Standard thread pattern which resulted saw the demise of several sizes demarcated in 1/32" increments.
Some say that there still exists equipment, such as drill presses and lathes which require tools built to the old standards, but I've never run across one. I would be curious to learn if anyone has ever found a use for a 31/32" socket. If you really have a need for one, let me know.
By-the-way, there isn't much out there on the old standards. Machinery's Handbook starts at and describes only the UNS standard although it alludes to its prehistory and development. The only source that anyone can cite are old tool catalogs from old-line companies like New Britain, Snap-on, S-K Wayne, etc. Someone compiled the following list of 1/32" sockets and their authorizing body:
[Begin Quote]
I've got a bunch of old sockets like that. I think I finally found the answer in some of my old catalogs.
Seems to be that there was a handful of "standards". The old 19, 25, and 31 correspond with the old U.S. standard. The 23 and 29 correspond with the old Mfr. standard. The 15, 21, and 27 correspond with the old Mfr. standard for square bolt heads and nuts.
Maybe this will help......
US Standard "Heavy" Hex bolts
19/32 = a 5/16 hex bolt by US standard
25/32= a 7/16 hex bolt ""
31/32= a 9/16 hex bolt ""
Mfr. Standard "Heavy" Hex bolts
17/32= a 5/16 hex bolt by Mfr. standard
23/32= a 7/16 ""
29/32= a 9/16""
Mfr. Standard Square bolts
15/32= a 5/16 SQUARE bolt by Mfr. standard
21/32= a 7/16 ""
27/32= a 9/16 ""
These are out of a mid 50's New Britain catalog but other old catalogs have same info.
An early 70's Snap on catalog no longer has the sizes in the chart. They have a column for Old U.S. and old SAE but no 32nd sizes.
They have a date for the American Standard Association sizes and that shows 1965.
To sum up.....they consolidated bolt sizes in the 60's and that is when the odd sizes disappeared. Unless you are working on something old you probably won't need one....at least not for it's intended application.
[End Quote]
It seems that this socket was made to fit a 9/16" "Heavy" Hex Nut or Bolt according to the US Standard which was current BEFORE World War II. During the war, what with the US trying to source parts for Britain as well as trying to use parts from them for assembly there was quite a bit of standardization which was formalized in 1949 or so. So that the Unified National Standard thread pattern which resulted saw the demise of several sizes demarcated in 1/32" increments.
Some say that there still exists equipment, such as drill presses and lathes which require tools built to the old standards, but I've never run across one. I would be curious to learn if anyone has ever found a use for a 31/32" socket. If you really have a need for one, let me know.
By-the-way, there isn't much out there on the old standards. Machinery's Handbook starts at and describes only the UNS standard although it alludes to its prehistory and development. The only source that anyone can cite are old tool catalogs from old-line companies like New Britain, Snap-on, S-K Wayne, etc. Someone compiled the following list of 1/32" sockets and their authorizing body:
[Begin Quote]
I've got a bunch of old sockets like that. I think I finally found the answer in some of my old catalogs.
Seems to be that there was a handful of "standards". The old 19, 25, and 31 correspond with the old U.S. standard. The 23 and 29 correspond with the old Mfr. standard. The 15, 21, and 27 correspond with the old Mfr. standard for square bolt heads and nuts.
Maybe this will help......
US Standard "Heavy" Hex bolts
19/32 = a 5/16 hex bolt by US standard
25/32= a 7/16 hex bolt ""
31/32= a 9/16 hex bolt ""
Mfr. Standard "Heavy" Hex bolts
17/32= a 5/16 hex bolt by Mfr. standard
23/32= a 7/16 ""
29/32= a 9/16""
Mfr. Standard Square bolts
15/32= a 5/16 SQUARE bolt by Mfr. standard
21/32= a 7/16 ""
27/32= a 9/16 ""
These are out of a mid 50's New Britain catalog but other old catalogs have same info.
An early 70's Snap on catalog no longer has the sizes in the chart. They have a column for Old U.S. and old SAE but no 32nd sizes.
They have a date for the American Standard Association sizes and that shows 1965.
To sum up.....they consolidated bolt sizes in the 60's and that is when the odd sizes disappeared. Unless you are working on something old you probably won't need one....at least not for it's intended application.
[End Quote]