View Full Version : Bending hollow box section
12-23-2003, 01:21 PM
what is the best way to bend box section without it crumpling
BRENT in 10-uh-C
12-23-2003, 01:34 PM
Can you fill it with sand and temporarily "cap" the ends? I have done it that way using some old sandblasting sand. I then used an old rim off of a truck to bend it around. Just heat it with a rosebud torch and work it slowly. Maybe someone knows a better way but that worked for me once.
12-23-2003, 01:39 PM
cheers for that, once it had cooled, did it contract and need reheating / rebending?
BRENT in 10-uh-C
12-23-2003, 01:57 PM
What I was bending was some radiuses for the front of a camper in the front leading edge. I was using 2x2 tubing but I would imagine that if you were using some big stuff it might shrink a tad, but it wouldn't be that big of a deal to experiment some.
01-04-2004, 12:16 PM
Another tip that i've used with success is cutting the tubing on both sides. The clamp to the bending die (whatever it maybe) then heat the same way as mentioned above and bend the piece closest to the die. Then heat the outer portion and bend it to the inside portion. Make sure you add extra material to the bend because the outside of the bend will be shorter. Once the outside bend is finished just weld the two cut areas back together and sand. This method is closest I have been able to get to a mandel bend. I have used the sand on round but not square or rectangular tubing I am going to try it sometime and see.
01-07-2004, 09:49 AM
When bending square or rectangular tubing, there really is no way to eliminate all of the "cupping" or kinking but there is a way to minimize it. First, you must first determine the amount of tubing the bend is going to take up. Then cut the tube in half on the sides (the length of the bend). After you have it cut the length of the bend, make another small cut at one end so that this section is only connected at one end. With your remaining larger section (the piece that has the notched section removed), clamp this in the die to be bent around and heat it thoroughly with a rosebud tip until cherry red. Slowly bend until desired radii is had. Then with the remaining section (that should still be sticking out straight) heat the same way and bend with pliers or whatever. After everything is bent the way you want, simply weld the entire seam back together on both sides and sand.
This method reduces the amount of cupping on the tubing much more than the sand packing technique but it is much more work!
I realize this sounds very confusing and is much easier when you see it done. I actually saw Ron Covell use this same technique in a Tube Bending Video. Hope this helped and sorry if I confused you more. :roll:
01-07-2004, 02:39 PM
I have not tried this personally but I would be tempted to try that on my Hossfeld Knock off bender.
That style bender works FANTASTIC on round material and I know they sell the dies for square and rectangle shapes. The dies are expensive, but if you did enough bending they'd be worth it.
My buddy bougth ONE set of dies and has scaled them up/down for additional sizes. I wussed out and bought them. <sob - sob>
Your mileage may vary
Jacin in Ohio
01-09-2004, 11:02 AM
You can use these Hossfeld Type benders and yes they do work quite well. But, you will have a higher degree of "cupping" on bot the inside and outside of the bend. I have a JD2 Model 3 Bender that I concerted to hydraulic recently and it will bend square but like I said, it will cup. The tighter the radius=more cupping. Same goes for larger square tubing, esp. if it has a tight radius. If you're not too concerned with this cupping then I would absolutely suggest the Hossfeld type of bending unit as it is simple and relativiely inexpensive.---Grant
There's a trick that I've used that is slow but yields excellent results. You need two people, a rosebud torch tip and a form that matches the inside radius you wish to achieve,plus a 6" or so tangent at the start of the curve. You start by clamping the piece or tacking it to the straight tangent section of the form. Leave your piece longer than you need as it will give you more leverage when you are pulling on it. The helper heats the outside of the piece. If you heat the portion next to the form or the person heating gets too far ahead of the person bending, it will cup on the inside and you will ruin it. Be patient and start with scrap as there is a whole lot of tequnique that needs to be developed here. How much of the material you need to heat and how hot to get it is the trick. I ruined quite a few pcs when I started doing this. When you get good, you can keep a very slow constant bend going, with your helper staying just ahead of you. This action works the best. I've bent 2x2x3/16 angle (both ways) and 2x2x1/8 sqare tube with this method with excellent results.
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