Anyone have an ingenious way to bend square tubing? I am thinking, make a pattern out of wood, capture the tubing, heat and bend around the cut out pattern. This is a home project and I am no expert in the field. I need to bend several pieces and have them all end up the same length also. Basically two 90 deg bends on both ends. The bend can be a 6" radius. Any ideas would be appreciated.
I've never tried it, but it's fairly common in the auto racing industry. I've seen rear frame rails made of 2" x 3" rect tube bent to different shapes. The manufacturers use what is called a mandrel bender which has a die that runs inside the tube to keep it from collapsing during the bend (they bend it cold).
I think it would be difficult to bend at home even with a bend jig and heated up as the inside would try to wrinkle, or the outside/side walls would likely want to collapse.
The only way to know for sure is to go out to your shop and try it. I've bent some other things in the past using a bending jig/fixture I made form scrap and found one secret is to put slow but constant tension as your making the bend...too quick a movement and you'll surely collapse the walls.
BTW, what size tube? what wall thickness? what material?
EDIT: One thing I thought of...I've hand bent 1/2" diameter aluminum tubing by packing the inside full of sand...this was cold bent.
I guess you could try and pack your tubing full of sand before bending in an attempt to keep if from collapsing...worth a shot.
There are benders that will do what you want, e.g. Hossfeld Universal Bender but the expense would be prohibitive. But, if a local metal shop had one, it might be worth paying them to do it.
Filling the tube with sand is a good option to try, but it must be sealed so the sand does not escape while bending which may be tricky if you want/need to bend hot.
I have had success with a technique called wrinkle bending although it was with round tubing not square. You will end up with a series of neatly spaced wrinkles. Basically, you heat a succession of small areas one at a time and bend the tube a few degrees (e.g. 5 wrinkles @ 18 degrees = 90 degree bend) for each individually heated area, allowing the previous area to cool before heating the next area. If careful, you can end up with a 90 degree bend without collapsing the tube. Of course you have to be able to tolerate the wrinkled appearance. Again, I've never tried this with square tubing so you may have to experiment.
I'll be curious to know how you finally solve the problem.
Ken
This isn't very ingenious, but I laid out the shape I wanted on a table, welded pieces of pipe to the table about the size of the radius required for corners to form a template. Filled the tubing with river sand; capped both ends; tack welded one end of tube to table; applied a reasonable amount of heat to tube and formed around my template. This also for a home project, but result was very satisfactory.
Thanks for all the good ideas. These will be supports for the roof of a stock trailer so I am not too concerned about ribbing the inside of the bend. Here's my plan unless someone has a better idea. Capture my bend pattern made out of wood between two pieces of 1/4" sheet metal by bolting it all together as a unit. I am bending 1" sq tubing so the wood will be just wide enough to allow the 1" inside between the sheet metal sides. There will also be a bolt or something to capture one end of the tubing against the wood form at the start of the bend radius. Heat evenly around the radius of the bend and slowly bend tubing to conform to the "mold" if you will. I will let you know how it turns out. Probably will be a week before I get to it though....
Just want to comment on the wood idea. Unless you work very fast, I believe that the heat from the tubing is going to char the wood.
Regards
Niekie
Niekie,
The heat will indeed char the wood
You'll need a can or two of water or a hose handy to put out the fire caused by the heat, but it is possible to make it work where one cannot fabricate a "real" tool. It's also a good idea to dump the wooden jig into a bucket or tub of water; it can continue to smoulder for a surprisingly long time.
Regards
d
I'm not sure of load or complexity of the shape of the bend.
I have tried several methods and use two of them with satisfactory results.
One involves cutting kerfs along the inside radius like slices of pie, heating and bending the tube (wihich would probably work cold as well) and welding the seams back together... this I use on larger and heavier sizes HSS tubes which I otherwise would be unable to work.
The other is to merely heat it and bend it to where I want it to go; never thought much about precisely HOW, it just seems to follow the pattern according to where I place the heat to soften the metal and increase its plasticity where required.
In any case I leave some extra "selvage" at either end and trim to appropriate precision after the bend is completed.
Regards
d
BTW I like the sand idea and will give it a try
If you are looking to build a trailer roof for a stock hauler, perhaps going at this project from a different angle will appeal to you. I have built a few camper trailers from the axel-up , what I used for roof support were the bows from a school bus roof,cheap, strong, and already made.
Only drawback is all of the rivits, but an air chisel makes short work of this.
Another solution that I came up with was to use pre-made steel "sweep" bends for electrical conduit, and to weld tabs to the bend where the roof needed to be attached. To bad I didn't think about the conduit bends before I chopped up the bus, could have saved lots of time.
Ed
Well I finally found time to work on the stock trailer. Got the top rail cut, clamped and ready to weld. Got the front top rail, gooseneck support pipes all cut clamped and ready to weld. Made a quick jig last night out of plywood to try and bend the 1" square tubing. I captured the form inside two pieces of 3/4" plywood in an effort to keep the tubing from flaring out on the sides. Yes I got some smoke when I stuck the hot tubing in but after a couple of times the smoke diminished. I think it would have worked if I had been able to keep the torch on the tubing but as the jig was wooden that wouldn’t work. I plan to cut some steel plate to capture the form (bend shape) in. This should allow me to keep heat on the tubing while applying pressure. I am going to check with a welding shop and see what they would charge to make me 3 or 4 of these. If they are not too expensive I will let them do it in an attempt to save some time. It will take me awhile to build this jig out of steel so it may be cost effective to have someone bend these for me. Now I have to pull the trailer up close to the garage so my welding leads will reach J
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