Bending steel tube

[Rotate]

It is possible to bend steel tube so that there is no distortion along the bend? Is this even physically possible? I can see that the tube wall will thin out where it's stretched but how do you shrink steel without causing wrinkles?

Albert

[George Hodge]

I've bent a lot of thinwall conduit with a bender,with great results.Check with an electrician friend,for a sample.

[lynnl]

I've bent 1" stuff with heat, with no noticeable wrinkles ... at least until it approached 90deg.

[timf]

i've heard of putting a spring in the tube to support it while it is bending, but i have not done it myself.
it would have to be plyable enough to get back out after you were done.
something like a soft rubber or polyurethane rod, real close to the i.d. might work.

[Mike Milbrand]

Use CERRO-BEND. It melts in boiling water. Plug one end of tubing. Pour in the CERROBEND. Let everything come to room temperature. Bend your tubing. Melt it out in boiling water. The stuff can be used a million times!

[John Hewett]

<font face="Verdana, Arial" size="2">Originally posted by Rotate:
It is possible to bend steel tube so that there is no distortion along the bend? Is this even physically possible? I can see that the tube wall will thin out where it's stretched but how do you shrink steel without causing wrinkles?

Albert</font>

You can fill it with sand, plug the ends,(not airtight) heat& bend.

[C. Tate]

The reason conduit does not wrinkle is because the CLR (center line radius) of the bend is very large compared to the diameter. As the CLR and the diameter approach 4 to 1 you start getting to a point where you have to support the wall of the tube in the bend. Tube bending shops use mandrels for this purpose they come primarily in two varieties the solid and the flexible. Check out this site for a good diagram http://www.mfginfo.com/machtool/bending/rotary.htm.

The home shop guy can use low mwlting point substances or even sand to achieve the same results. If you try to air bend closer than 2 to 1 you will probably have poor results even with something in the tube.

[Cuttingedge]

Rotate:

What diameter,thickness angle of bend are you going to need to bend in steel tubing. I have bent a lot of EMT or thin wall tubing with a conduit bender. Just don't try to bend it too much to quick. For thickwall I use a hydrolic bender with dies. For 12 to 20 gage steel 1/2" through 1 1/4 inch I use a Shop Outfitters model 2516-H Compact Bender. I also bend alot of square tubing and it is distorted on the inside radius.
Good luck.
Cuttingedge

[Thrud]

Albert

CT is right - the mandrel benders do a beautiful job (CNC!) and are used for critical applications like reactors. Filling with sand or the cerro metal works but works best with seamless tubing. The seam welded stuff will split on the seam sometimes.


Small diameter EMT starts life out as special killed cold rolled (normally used for deep drawing applications) to make it easier to bend manually in the field and very unlikely to fail when bent(under normal electrical applications). It is not strong enough for roll cages - use 41xx for that.

[This message has been edited by Thrud (edited 08-01-2002).]

[trap]

41xx ??? is that chrome moly ???