How was this monkey wrench made?

Hi folks,
Happy New Year!
I have a challenge for everyone. I've just bought an old monkey wrench.
I bought it because I couldn't figure out how it had been made, and I
wanted to know. It's marked "Trimo" and was made by the Trimont
Manufacturing Co. of Roxbury, Massachusetts. Someone here might have the
same wrench.
Anyway, the wrench has an approximately rectangular hollow channel in
which the movable jaw slides. The channel has closed sides, i.e., it
isn't a T-slot. The wrench appears to be forged. The movable jaw is
marked "Drop Forged", although the fixed jaw isn't.
There is a line around the whole of the wrench, which appears to have
been made at the junction between the forging dies. The line also goes
down the back wall of the hollow channel.
I'm puzzled because the channel has sharp corners. If the corners were
radiused, I could imagine that the body of the wrench was a solid
forging, which later had the channel cut using an end mill or small
grinding wheel. But the corners are sharp.
There are no visible machining or grinding marks inside the channel.
I can only think that perhaps:
(i) The channel was punched out in a secondary forging operation.
(ii) The channel was created in a complex forging (possibly forge
welding) operation designed to make hollow parts.
(iii) The body of the wrench is actually a sand casting.
I'm inclined to favour option (i). I'd be interested to hear what other
people think.
I even checked the patent listed on the wrench, but it says nothing
about how the body is made.
Here are some pictures:
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Best wishes,
Chris
Reply to
Christopher Tidy
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The channel was broached.
Cheers Trevor Jones
Reply to
Trevor Jones
Probably after being hot-punched in a secondary forging operation. The whole body could be forged and punched in two hits.
-- Ed Huntress
Reply to
Ed Huntress
Thanks for the thoughts. That was my own best guess.
I'm a little surprised that it's possible to broach a deep channel with such thin walls (only about 3/32" thick) without everything getting mangled. Guess the key must be getting it hot enough.
Best wishes,
Chris
Reply to
Christopher Tidy
Production broaching is not much like the kind we do in hobby work. The broach itself looks more like a long, extremely coarse tapered file -- some as long as twenty feet or so -- with each successive tooth cutting a thousanth or three more than the last one, typically cutting on all sides at once (or not, depending on the job -- some cut on only one side at a time). They come in two general types: pull-broaches and push-broaches. They were made from a single piece of tool steel but recent ones have replaceable inserts.
The broaching likely was done cold. The rough-punched body would be held and supported in a fixture. Designing a feature for support is an important part of designing the forging.
-- Ed Huntress
Reply to
Ed Huntress
Thanks, Ed. That's interesting. Does anyone have a picture of one of those broaches?
How did they make the hole into which the broach was inserted? With a twist drill?
Best wishes,
Chris
Reply to
Christopher Tidy
I think I found one:
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Chris
Reply to
Christopher Tidy
Here are some photos and descriptions. Google "pull broach" and you'll get more than you ever wanted to know:
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Pull broaches are a lot longer, but you can search "push broach" to round out the picture. Your wrench likely was push-broached.
The holes in forgings like that are usually pierced with a piercing punch while the metal is red hot. That was the "second hit" I was talking about. This is a carryover from the days of blacksmithing. Hot-piercing is a common process in forging all sorts of products, whether by hand or by machine.
-- Ed Huntress
Reply to
Ed Huntress
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Thanks, Ed. I've now got the explanation I wanted.
Best wishes,
Chris
Reply to
Christopher Tidy
Yeah, that's it. I've seen them as big around as your thigh, and nearly 20 feet long. That one machined the internal teeth on the ring of a planetary gearset in one pull -- maybe five to ten seconds.
-- Ed Huntress
Reply to
Ed Huntress
That isn't a monkey wrench. It is the tool before a Crescent. Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net TSRA, Life; NRA LOH & Patron Member, Golden Eagle, Patriot's Medal. NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member.
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Christ> Hi folks,
Reply to
Martin H. Eastburn
It says "10 inch M.W." on it.
Chris
Reply to
Christopher Tidy
That sounds awesome if you need to cut internal gear teeth of a particular size. I'd certainly love to see a machine like that in action!
Best wishes,
Chris
Reply to
Christopher Tidy
Stick ta ya guns, Chris. or go here:
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Of course ya owe me a pint now. :-)
Tom
Reply to
Tom
Fine - it has the pipe wrench design but flats. The monkey wrenches I am used to had pipe jaws. These might be a variant that tried to take Crescent on. I think I have a variant in another direction.
Martin
Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net TSRA, Life; NRA LOH & Patron Member, Golden Eagle, Patriot's Medal. NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member.
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Christ>> That isn't a monkey wrench. It is the tool before a Crescent.
Reply to
Martin H. Eastburn
Another thing I've been wondering about: is the broach inserted into an oversize hole and firmly held by guide rails, or is the broach self-centring in a tight pilot hole? In other words, what determines the precise location of the broached hole?
Best wishes,
Chris
Reply to
Christopher Tidy
Push broaches are usually located with their own guides, but they can be free-floating in jobs for which precise location is not important. In the case of a an old wrench, it could be free-floating. The punched hole was close enough.
The hole is undersize, not oversize. The leading end of the broach is undersize, and then the teeth progressively cut the hole to size.
-- Ed Huntress
Reply to
Ed Huntress
Thanks. It's interesting to know that you can get both kinds. Looking at the wrench, the hole appears to be quite precisely located, so I imagine there was some kind of guide.
I meant oversize relative to the small end of the broach, not the finished hole.
Best wishes,
Chris
Reply to
Christopher Tidy

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