Seamus

Upsetting to one side of a square bar

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Don't find a technique forum, so posting here.
Apologies if this isn't the right forum.

How do you upset to one side of a square rod?

I've wanted to make a pair of holdfasts for a joiners workbench
since I first read about a guy named Rob Tarule
using them in an article in Fine Woodworking.
They're very fast and flexible compared to a vise.

Since I read that article, Chris Schwarz has gone on a tear
and popularized the Roubo workbench, so much so that
you can't hardly swing a dead possum without hitting
one on the Interwebs.

Peter Ross recently made a close if not exact replica
of the holdfast illustrated in André Jacob Roubo's
L'Art du Menuisier, the book that started the whole thing,
for Schwarz and you can see the original illustration here





and Ross' results here

http://www.popularwoodworking.com/woodworking-blogs/chris-schwarz-blog/workbenches/that%E2%80%99s-not-a-holdfast



and some "work in progress" shots here:

http://www.popularwoodworking.com/woodworking-blogs/chris-schwarz-blog/workbenches/straight-from-the-frenchmans-mouth

In the first illustration of Ross working on the bar
it looks to me like he has upset on one side
midway down the bar. The upset is to make
the mass for the shoulder of the head.

I've upset on end, but not midway and not
to one side like that. What's the technique?

I know you can make a holdfast by bending
but that's not what I'm interested in.

Thanks for any suggestions

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very much the same way you just do it in the middle heat the section you want cool either side of the heat and compress. Driving the metal on the anvil or hit it with your hammer. an other option is start off with parent stock the size you want and taper down each side to the shape you want.

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I would do an upset in the middle of the bar by taking a localized heat, quenching the heat shorter in length if needed. Obviously keeping an upset even is necessary, or the bar bends prematurely. After the upset is complete, I would then hammer the stock down on either side of the upset making it offset. Naturally I would choose the side with the least material already to make flat. When you bend in the upset area a short in length, high heat will be required so the fattest part of the material will want to bend easily, compared to the thinner material.

In one of the texts from the early 1900's I downloaded it describes taking an upset, making the bend with the upset more or less symmetrical, then finishing the upset by upsetting the bend to make the outside corner square, and the inside corner rounded.

Phil

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For that particular design it would usually be easiest to make the square corner first and then upset it from both sides. It would be considerably more difficult to upset before bending (IMO). You basically just make the bend and square it up then upset first from one side then the other pushing metal into the interior of the corner as you go and continually controlling the side thickness. Get the corner made and upset before you draw out the spring and clamp pad. We've had other threads about this so try a search too. If you try to upset first you are going to have a thicker area right where you want to make the bend... and the bar will want to bend anywhere else BUT where you want it to.

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If you read the article attached with the photos of Peter forging the piece you will see that it says he had to search for a piece of 2-1/2" round inorder to start forging the hold down.

There would be no reason to upset the corner starting with such a large stock size. In the first photo you can see that after forging to a rectangular cross section he has forged a taper away from where he is forming the corner....no upsetting involved. In the second pic he is starting the bend with the heat properly located in the bend area "only" before forging the taper,thus eliminating the problem mentioned by bigfoot.

The metal is kept to the outside for the corner by forging the material on both ends down and away from where you want the corner to be.

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Looking at the photos in the article, it looks to me like he started with some thick rectangular stock and drew down both ends, leaving a thick portion for forming the corner. Note how rough the stock appears near the tongs.... this would seem to indicate a lot of hammer strikes to bring the shaft down and round it off.

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Why does it have to be square stock? Looks like the hole in the bench is round. Why can't the bend be round?

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Why does it have to be square stock? Looks like the hole in the bench is round. Why can't the bend be round?


Good question. The bend can be round, but It tends to be easier to taper a square bar than a round one. The common practice to taper the end of a round bar would be to square up that end of a round bar, then taper that end, then forge that end to octagonal, then forge back to round. On one of my benches I have a hold-down with a round bend.

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I was going to comment on the 2 1/2 inches bit, but you are going to make the tool to suit your anvil or bench, so why dwell on it? For my anvil, I would need to fit a 1/2 inch pritchel. I would choose the size to fit my workbench, or since my current workbench does not have holes I would choose a convenient and suitable size requiring my bench to be drilled.

If I was making for a platen table, then that is large stock.
http://www.iforgeiron.com/topic/23440-dang-dogs/

Phil

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As already mentioned, Regardless of the square/round stock, by hand, its easier to draw steel square, then shape as required.
and Starting with the bulk where required, for the reinforced bend, in lue of upsetting, makes sense.
Maybe he just didnt think to upset for this bend, then move the steel into the corner required, or did, and thought it easier to come down to the size required, with the larger starting stock. Nice job regardless of method.
To upset for this type of bend, heat the middle of a piece of bar as you would for an end upset, and upset the middle section by striking a cold end, to the required size bulge, start your bend, on a mandril to retain the inside radius, then strike/create the flats either side of the sharp outside corner. Saying it now, I would go the larger starting stock.

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