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Hi All i hope i am doing this in the correct way, i am new to forums, i need to form a 1.5m (about 4' )  diameter circle out of 12" square stock, i need it to be as close to perfect as posible. at the moment all i think of is to cut a template out of 3/4" ply and try to bend some 30x6mm flat stock around it to make a form, but at 30 quid a shot for the ply and 12 for the flat bar its quite an expensive form for a 1 off,  any ideas would be massively appreciated.  

Thanks in advance.

circle 3.jpg

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12" square stock is pretty large and heavy!!  You might be better off going to an industrial metal fabrication shop for something that big.  How in the world would you plan on handling something that large, anyway?

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Did you mean 1/2" square stock?  So you want to make a 4 foot ring out of 1/2" square stock?

Probably in industry it would be done on a ring roller, two rolls on the bottom and an adjustable third one - a triangle configuration.  Lowering the third roller gives a tighter radius.

And I have seen a similar configuration of round bars on a fly press to bend the stock bit by bit (generally cold) until the full circle is formed. Maybe you could do something similar to that with a couple blocks and a hammer and a template to judge whether you're on track or not?

-- Dave

 

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You only need to make a form that's got the right radius.  No need to make the complete circle as a form.  With chalk and a string, you can layout the radius on the floor, or scratch it in the dirt.

 

Then finagle the bar to shape.  If necessary, cut the rim piece into sections so it's more easily handled.

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Hi and welcome!

What VaughnT said if you want to do it on your own.

If I were you I tried to look around and find a shop that has a roller. I don't think they charge that much for a simple roll. 

Bests:

Gergely

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harbor freight has an adjustable roller you can buy, its about $150 last time I bought one.  I'm not generally a HF fan, but it was for a single job rolling some tube, I needed to roll 5  12" rings out of 1" copper.  I figured it would be a consumable tool and not last, but its been hanging around the shop and used quite a bit.  I took the time to mill a few specific dies, but theres a number of sites that sell various milled dies for it online, but for 1/2 square just use the flat dies that come with it.  youll loose about 6" of material on each end that wont bend into a radius so for a 4' dia ring youll need about 13' getting you 1 ring per 20' stick of material unless you weld the drops together. 

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When my Dad made the anodizing tanks for one of the air bases he was stationed at he just used blocks to make the large diameter coils. He clamped the blocks so that when he drove the tubing through them they got the curve going, then all he had to do was just keep driving more tubing into them to make the coil. Watch a video on how coil springs are made. Or some on making rings.... ;)

For this project you can also figure out some spacing, and how much to bend at each measurement to get the circle--like a sheet metal shop does in a press brake for some items. Once it is a circle, weld the ends, and smooth the kinks out. The closer the bends the smoother the radius.

 

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  • 3 weeks later...

hi Thanks for all your help

On 23/3/2017 at 0:49 PM, J said:

hi all, thanks for all your advice it is much appreciated, i ended up making a simple roller with some left over scaffolding and a car jack. i also changed the design and used 30x6mm for the outer rim and 12mm square for the rest, here is a few pics of the project. Thanks again  .

 

wheel 3.jpg

wheel2.jpg

wheel1.jpg

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Thanks for all your comments, this was my first project other than fire side tool sets, and trivets. As i said at the start i am new to the whole forum concept, I really hope all you old timers  know how much it means to people like me, that there is some where to ask questions.

 

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Only just saw this thread. Good job with that window grill.

It's disappointing that no one suggested to make the circle as it is done, that is with a ball peen hammer on the open post vise, little by little and checking on a circle drawn on paper.  ... oh well. All's well that ends well. 

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"As it is done"  you mean using a ring roller or using the ski jump tool in the hardy where you bridge the workpiece on it and the anvil and tap the unsupported section reheating and re-working to get the hoop you need? I've also seen it done using a flypress with a projecting nose and two bars spaced on the base.  I don't know anyone who does it in the postvise.

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Cold not hot, on the post vice open jaws. Tap in the center as you push forward slowly, you get the circle you want. How much you open the jaws, and what size hammer will depend on the dimensions of the flat bar. It requires several passess and checking on a pattern. 

If you want to do it hot, you will need to make a jig as you do to make a scroll, but if you master making this cold you won't bother making a jig. 

That is how my old Italian master did it and this is how I learned to do it and did it for a long time until the decorative globes we used to make by the hundreds went out of fashion. 

It takes some time and of course a bending machine will do it quicker. A big circle that allows to hammer inside the circle like this one is easier than a smaller circle. 

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