Standard and Non-standard wrenches

WizardOfBoz · Feb 15, 2018

I have a bunch of old (1950s-1970s) Armstrong combination wrenches I like. I've a pretty complete set up to about an inch, and have some larger ones (like a 2 incher, useful for use on evildoers who invade my house, but not much else). In looking at the missing wrenches I looked up standard bolt head sizes.

I noted that I have two wrenches, 19/32 and 25/32 inch, that are not standards, at least SAE standards. There's a spot in Armstrong's model number sequence for these wrenches (indicating that they were made as standards), so I guess my question is: what are these wrenches used on? Is it something like AN bolt intermediate sizes or something?

johnoder · Feb 15, 2018

Peculiar automotive engine fasteners. Not included in your pair is the 21/32 for Model A Ford connecting rod nuts - if I recall correctly

First wrenched on a Model A 64 years ago

bosleyjr said:
I have a bunch of old (1950s-1970s) Armstrong combination wrenches I like. I've a pretty complete set up to about an inch, and have some larger ones (like a 2 incher, useful for use on evildoers who invade my house, but not much else). In looking at the missing wrenches I looked up standard bolt head sizes.

I noted that I have two wrenches, 19/32 and 25/32 inch, that are not standards, at least SAE standards. There's a spot in Armstrong's model number sequence for these wrenches (indicating that they were made as standards), so I guess my question is: what are these wrenches used on? Is it something like AN bolt intermediate sizes or something?

Rudd · Feb 15, 2018

Fun reading:
Progress is fine, but it's gone on for too long.: The evolution of standard wrench sizes
States those were used on 5/16" and 7/16" bolts at one point.
I have to think that those openings persisted for some time, I've got what I think is a not so old 25/32 wrench, and I think I can recall using it on a vehicle.
I don't recall using oddball sizes when I worked at the bomber plant, and there were plenty of AN fasteners - then again, my memory may be faulty.

Gordon Heaton · Feb 15, 2018

I have a handful of Proto sockets in similar sizes. I worked for a NAPA store in the 70's and at that time you could get a full set in 32nds if I remember correctly. I'd guess it was just so you could get a good fit even on an off-standard or worn fastener. All of the oddballs I have are thin-walled 12pt sockets.

Limy Sami · Feb 15, 2018

Those two sizes also ''reasonably'' fit commercial quality 3/6 & 7/16 Whitworth nuts and were included in many US made wrench sets exported to the UK,plus of course we had the model T onwards Fords built over here .

Fastenerdata - BSW Whitworth Hexagon Full Nut Grade-A-Steel BS183 - BSW - Hexagon Full Nut - NUTS - DIMENSIONS - Fastener Specifications

John Garner · Feb 15, 2018

bosleyjr --

As I have heard the story, back before World War II, the across-flats dimensions of bolt heads in the United States were a) 1 1/2 x screwthread Major Diameter for U S Standard fasteners, and b) 1 1/2 x screwthread Major Diameter + 1/8 inch for U S Heavy fasteners. As a result, heads of fasteners having odd-sixteenths threads had odd-thirty-seconds heads.

So, for example, a 7/16 inch threaded fastener would have a 1 1/2 x 7/16 inch = 21/32 inch head if U S Standard, 25/32 inch head if U S Heavy.

John

BobRenz · Feb 15, 2018

I have some Armstrong wrenches in my collection as well. THANK YOU for clearing up where a 25/32 wrench could have been used. I've wondered about that for years.

Tony Quiring · Feb 15, 2018

Have an old ranch windmill in the back yard/ 35 ft tower and 10 ft disk.

The tower came from an old farm and dates way back and the bolts were some x/32 sized head and we had the wrench for it.

Sent from my SAMSUNG-SGH-I337Z using Tapatalk

Leg17 · Feb 15, 2018

31/32" is the old U.S.S. standard for 9/16" bolt/nut.
25/32" is the old U.S.S. standard for 7/16" bolt/nut.
19/32" is the old U.S.S. standard for 5/16" bolt/nut.

wheels17 · Feb 15, 2018

I have some older wrenches that threw me for a loop. I received them in a box of other stuff, cleaned them up, and put them in the wrench drawer. One day I grabbed the 1/4 and it was way off. Upon closer inspection, the wrenches were labeled by the size of bolt, not the size of the wrench opening.

3/16 USS is about 7/16
1/4 is about 1/2
5/16 is about 19/32

I found this after a bit, very interesting: Standard Numbers for Open-End Wrenches

"In the late 19th and early 20th centuries, wrench sizes were commonly named by the nominal size of the bolts whose nuts they fit, rather than the size (across the flats) of the nuts themselves"

The chart on that page also shows standard wrenches with openings of 13/32,19/32,25/32,and 31/32.

The large sizes have some odd progressions as well. I have the ones in bold.

1, 1 1/16, 1 1/8, 1 3/16, 1 1/4, 1 5/16, 1 3/8, 1 7/16, 1 1/2, 1 5/8, 1 11/16, 1 3/4, 1 13/16, 1 7/8, and 2.

It's nice not having to use a pipe wrench on trailer balls.

dian · Feb 16, 2018

and today, in the u.s. automotive world, it seem to be the other way around: metric screws are not referred to by diameter but by the wrench size.

Limy Sami · Feb 16, 2018

On the subject of wrench / AF of nut & bolt hex sizes.

Over here in the UK at least?? 7/16 UNF & UNC have always been the odd man out, the bolt heads being 5/8, and the nuts 11/16 AF

Yet (from memory) in all the other common sizes up 5/8 both nut and bolt hexs are the same.

DDoug · Feb 16, 2018

Maybe, just maybe for "Hot Dipped Galvanized" ?

kenton · Feb 16, 2018

Those would be very close to 15mm and 20mm. Perhaps those metric sizes used to be commonly used on an imported item. For some reason I have it in my head that spark plugs were originally all metric so maybe something with that?

Newman109 · Feb 16, 2018

kenton said:
Those would be very close to 15mm and 20mm. Perhaps those metric sizes used to be commonly used on an imported item. For some reason I have it in my head that spark plugs were originally all metric so maybe something with that?

Beat me to it. I'd just re-mark the wrenches and keep them.

Limy Sami · Feb 16, 2018

camscan said:
From memory, from memory? Leave it out dad, you lost your marbles before I lost my virginity.

Less of your lip sunshine - end of year bonus time is approaching!! ..........and the board has no desire whatsoever to hear of your frankly disgusting sex life.

John Garner · Feb 16, 2018

dian --

I suspect that wrench-benders and machinists have used different terms to describe fastener sizes starting at about the time the mechanics of the 1800s started to think of themselves as one or the other. It's been fifty years since I starting hanging-out in machine shops, and one of the first things I learned was that wrench-benders quantified fastener sizes in terms of the wrench opening, while machinists spoke of thread sizes. (Back then, the wrench-benders called themselves "mechanics", which most of them today seem to regard as an insult . . . they are "technicians".)

John

maynah · Feb 16, 2018

I have wondered about a Colchester Lathe wrench I have. It's marked 7/16 UNC and 3/8 UNC.
Now I understand.
The 3/8 is about .574" and the 7/16 is .710".

JST · Feb 16, 2018

If I recall correctly, one of those is just right for the nuts holding the compound of an older Logan. Probably from being the old standard for USS 5/16" nuts.

Leg17 · Feb 16, 2018

Limy Sami said:
On the subject of wrench / AF of nut & bolt hex sizes.

Over here in the UK at least?? 7/16 UNF & UNC have always been the odd man out, the bolt heads being 5/8, and the nuts 11/16 AF

Yet (from memory) in all the other common sizes up 5/8 both nut and bolt hexs are the same.

My memory is as bad as yours and I think it may still be so in the States as well.

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