I need to make a 24" diameter (outside) circle out of 1" square 16ga. tubing. This will be the focal point of a decorative tall gate. Within will be a Lauburu (kind of a four leaf clover), which is the national symbol of the Basque people.
I have the following tools: Acetylene torch (in case I need to bend it hot)
500 lb. anvil metal band saw (could make a million slits, bend and weld back together) Lathe (could make dies for the 1" tubing and build a three wheel bender).
This project has to look good. If I need to send it out and have it commercially fabricated, so be it, but, I would rather buy/make tools and do it myself.
I made a bender to form 1/2" square 16 gauge tubing and it works pretty well. I started with a 1" thick by 6" round slice of steel, and turned a 1/2" wide by 1/2" deep slot in it. It is basically an overgrown Imperial type tubing bender, like I used to use for 1/4" and 1/2" round tubing, but with a different die. I have been told that you can bend square tubing at a radius of about 4 X or greater the tubing size without heat. From this a minimum radius would be 4" for your 1" tubing. If you make one, I learned a couple of things: Leave a little draft on the side walls of the die. A 1.005" slot at the bottom should be a 1.015" or so slot at the outside of the slot.
Pay attention to the finish of the bottom and the walls of the slot BEFORE you cut the side of and the die is not a complete circle! the bottom of the die only needs to be flat. The sides need to have a good smooth finish or it will be difficult to get bent pieces out of the die. The tube will swell out against the walls and really get a grip on any tooling marks you leave.
It worked well enough that I used it to fabricate some furniture for our living room with it.
I can post a picture of the bender to the dropbox if you want.
Yes, call Leigh at MarMachine and order up one of his tubing rollers.
I think they are only $2500 or so. I may be wrong of course. But they work marvelously well
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Bob, Thanks for the good advice. I understand your method completely. But, seems like the result of using your bender would not guarantee me a 24" diameter circle, but, instead, a series of arcs that will be approximate. Because of the design that will go inside of the circle, any malformation (of the circle) will be real obvious and unacceptable. HOWEVER, maybe it's just a matter of practice. I will start with my conduit bender and see if I can learn to form a 24" diameter out of 1/2" conduit. When successful, I will move up to 1" conduit and after that, make the tool which you recommend to use on the square tubing. Where you able to bend with any precision? Thanks, Ivan
If I had to make that, I would go get 2 23-7/8" circles with 23-1/8" holes centered in them lasercut from 1/8" sheet steel. Then I'd cut up 2 lengths of
1/8x1" strip, and roll a 24" circle and a 23" circle. Then I'd weld the 4 pieces together and sand everything smooth.
You left out one really important detail: how the gate will be finished. If it's going to be painted you can just assemble the circle with solid tacks and fill the cracks with fine autobody putty, sand and prime.
It may be possible to roll a neat 24" circle from 16 ga. steel tubing (this *is* steel, right?) but I sure couldn't do it.
Hey Grant, the above is an EXCELLENT idea!!!!!!!!!!! And yes, the gate will be painted, ergo, I could use body putty. NEVER would have thought of that.
Thanks you so much. I do have a plasma cutter, dare I try to cut this out myself??? As you said, a little welding and putty would take care of any mistakes. Will look in the drop box to see if anybody has any suggestions for a circle cutter attachment for the plasma.
(Hope that rainy period in Washington didn't affect too badly. We got pretty lucky here in the Portland area.
I used to own a wrought iron business. I bought a mechanical roller bender for $3300, and that was back in 1985. It was great for making bends, but it reached its limits before it could make the 24" circle you need out of 1".
I did have one project where I had to have some 12" radiuses made, and had an outfit in Southern California do it. They used a mandrel (?) bender. That is one that uses a C shaped receiver, and a ram to push the tubing into the receiver. On the back side of the tubing, there is an indentation about a half a fingertip deep.
As stated, if you have a plasma cutter, it would not be hard to just cut some plate, and make your own. Drill a hole and just use a piece of wire to make them consistent. Or cut one guide piece out of plate, and then use it as a template to guide your torch head for the rest. The better you cut, the less finishing you will have to do.
Doing it with a plasma cutter will be a lot easier and produce a much better finished piece than with the tubing. I spent a lot of hours trying and learning about the characteristics of bending square tubing before I bought the Boulden and Lawson bender. I used it for years, made lots of awnings, wrought iron, and money with it before selling the business. Bending square tubing can be done, but doing it and having it look right is quite tricky.
Post some pics when you get done.
I hope to be getting into CNC plasma cutting this coming year. After then, I will probably be doing some of these things for people in the newsgroup.
Hi Ivan, I was able to get good precision with the bender I built, but I was bending stuff at the radius of the bender. It would be quite difficult to bend a radius larger than the bender radius and have it come out smooth. I think that a 3 roller arrangement with one of the rollers grooved as I described and two flat rollers would be the answer for a larger radius. I have been holding off building a 1" bender until I get a better idea on this.
The plasma cut circles is probably the best idea. If you are of a mind to, you could use your lathe to make the bits for a circle cutter guide for the plasma cutter head.
I saw your note of living in the Portland area, we lived in Camas, Washington for about 5 years.
Hi Ivan, Another way to do this is to get a length of square tubing a bit longer than needed to bend into the circle, and bandsaw it in half lenghtwise, to give you two equal channel sections. Bend the inner piece around an mdf form, it's much easier to work when it's just a channel, you can use a hammer and dolly to keep the sides straight. Then tack the outer section to it, you may need to heat its flanges to get them to shrink as you go. You can then just fill and sand the flat side surfaces, the inner and outer corners should be OK.
If you are going to do much fabricating with tubing, I highly recommend Ron Covell's video on the subject.
I have used just a strip of wood for a circle cutter....make a hole in one end to fit the tip of your plasma torch, put the pivot point in the appropriate place and cut away. Its not fancy or adjustable, but for a few cuts works just great....
I bought a roller guide for a cutting torch from Harbor Freight. I was able to bore the holder out a bit on the lathe and my Thermal Dynamics plasma torch fit very nicely. I replaced one of the roller legs with a length of 1/4" square stock and added a adjustable pin and it cuts circles of any size (the length of the square stock). With both rollers in place, it follows a stright guide and makes very nice cuts.
I made my own 3 roller arrangement with one of the rollers adjustable up and down... The rollers are 3" round X 14" long solid metal powered by a gear motor that's reversible .. I bend 2" sq.12 ga. tubing with no problem... It kinda flatens it out a little so it's not really sq. when I'm finishes but thats OK with me... I can bend 4" x 1/2" solid bar stock with this machine with no heat... If you make a machine like this don't forget to make a way to open the top roller to get your circle out of the machine after its finished...