How can I bend flat bar into a circle?

Years ago I saw blacksmiths cold reverse the curve in an old Ford rear axle main spring. (This put the shakles bolt holes on the top and ended up lowering the rear). With chalk, they drew the curve they wanted (the original curve) on a sheet of steel. They took a big block of steel that had a vee in it, and 3 men did the job. One held a 'handled blunt chisel' (like a rounded axe). One had the sledge hammer, and the last one worked the spring. They started on one end of the spring, and gently beat the chisel on the spring over the vee in the big block. Going from one end to the other, eventually, the spring was straight. They kept this up and eventually the spring started to recurve. Finally, when they would get to the other end, they would check the recurve against the chald line. They kept at this until the recurved the spring matched the chalk line. Easier to take it to a foundry and have it rolled.

A ring roller - basically 3 wheels where one wheel can be squeezed down between the other two, and one or all of them can be driven to run the metal through - gradually increasing the offset until the desired circle is acheived.

If you're going with a wooden form, try a form with holes that permit you to use an absurd number of c-clamps to get the band clamped into place for the weld. Wet the form before welding to keep the fire down.

"Ecnerwal" wrote A ring roller - basically 3 wheels where one wheel can be squeezed down between the other two (clip) ^^^^^^^^^^^ A ring roller will work, but it will leave the ends of each piece straight. Since you already have a HF "Hossfeld" type bender, I would use it to do the ends, and then run each piece through a ring roller.

Since this only has to be eyeball perfect, you might try bending an imperfect ring on the HF bender, welding the ends, and then going back to the bender and truing it up. I think you will find that the bender will sort of "talk to you" about what adjustments are needed. If the handle moves too far, you will know that is a part that is bent too much. So keep tweaking the parts that are not bent enough.

i've tack welded one end to a pipe, then heated the bar and hammered it around to the other end welding the two ends together, then grind the tack on the pipe. good luck, walt

I know this is a welding group so I *should* offer a welding-based solution, but ... if you have access to a bandsaw, cutting the rings out of a piece of 3" or 4" schedule 40 pipe might be an easier way to get what you want, assuming you have some leeway with the 12" circumference. Or you could set up a jig and cut them out with a cutting torch for a slightly textured edge. If you insist on rolling the pieces, you know that the ends are the hardest parts to form properly, so one approach is to roll two pieces slightly larger than a semicircle, cut off the ends to form two semicircles, and then weld them together.

Bert

"Dante M. Cat>I want to bend 12" long pieces of 1/8" X 1/2" mild steel into a circle and

Always beend the ends first, using a hammer and something round or a vise, then bend your rings.

You can buy a small simple ring roller for about $50 from Harbor frieght.

There is more than one way to do this. 1) Buy a tool...get a circle roller, and simply run the metal through it several times, until it ends up the "right" size. 2) Weld up a jig consisting of a couple of 3/4" rods, about 3" long, to a thick base. Space them a bit apart...say...half an inch? Use them as pivots to slowly work bends into the strip of metal until it is the "right" shape. In both cases, build a template to adjust it to the correct size. It is always easier to spring a circle OUT a bit, and have it still work ok, then it is to pull the ends IN to each other. Go slightly over 360 degrees and then cut the ends to fit perfectly.

Regards. Dave Mundt

It really depends on how many you are going to make.

If you only need a few, then you dont want to waste a lot of time making your tooling. Just wrap it around a pipe and hammer it a few times.

If you are making thousands, then I'll tell you what "I" would do. Make a small tube furnace out of ceramic fiber in the shape of a tube. Both ends of the tube are open. You can feed your stock continuously, and it comes out hot on the other side. As it's coming out, simply wind it around a piece of pipe in the shape of a spring. Then, after cooling, you make one long cut along the length of it and you'll have buckets full of rings. Or, you could cut them oen by one with a bolt cutter or whatever.

Judging from the picture you provided, it should be possible to do this without heating at all. In your case you could also wrap the steel into a spring shape and THEN heat top red hot and allow to cool.

Will

Or go to:

-- Regards, Carl Ijames carl.ijames at verizon.net

By looking at the picture the ring is only about 4 inches in diamater ...I think the absolute easiest way would be to cut half inch long pieces of 4 inch tubing , then you have zero forming to do. If you insist on rolling pieces, just roll them to a bigger diamater and cut the flat ends off and weld it together.

Good Luck...glad I was able to help on the leg portion!

We make a lot of rings like this where I work and they are mostly used for mounting booys onto grain silos; they have to be really round. We have numerous benders of different designs, and the three wheel ones are pretty good, but end up leaving the last part of the circle flat. For a lot of them, we work out the *diameter* of the circle from the radius, then make your flat about 300mm longer. Bend it with whatever you have so you get a lot of overlap, then cut some of each end off so that the diameter is right. Now you have the right size circle, it just isnt perfectly round, but it a good start.

Weld them together, then find out which part of the circle is 'high'. Don't cring. Now throw it at the ground so this part hits. Repeat as necessary until you have a perfect circle. Use a jig to find when its round and when its out.

You might laugh, but this is just about the best and easiest way of getting a perfect circle. A lot of custom made rims are 'trued' in this way too.

Shaun

How about take 4" diameter schedule 40 pipe, put it into your saw and cut 12 pieces 1/2" long? Much quicker and cheaper too.

replying to Shaun, Gregk wrote: I found this thread of this forum looking for ways to make my 3", 2" and 1" flat bar into 32", 30", and 20" circles. I have access to a welder, but no metal bender or torch. I do not want it to look hammered and I want perfect circles.

The method of over-bending then welding and hammering it out cold, Is this a good method for big circles as well, it seems like you would have to be super gentle to not make it an oval each time. Thanks

Not knowing your circumstances, this may not be useful information, but...

Making good, smooth circles out of bar like that, by hand, is something about which I would be very skeptical. That's a job for a Buffalo or other tube/pipe/section bender. Even that takes some skill:

OK ... there is no such thing as a perfect circle - there are only circles with tolerances. You could have circles that vary by +- .5" in diameter (pretty good), +-.25, .1 (Very good), .01 (exceptional), etc.

The welding/hammering is not going to work very well for a beginner. To get anything reasonably close to a "perfect circle", you're going to need something like this:

Of course, if you could elaborate on what you want to do, we could give better answers.

Bob