Exhaust pipe bending.

[Zac]

I recently bought a 12 ton pipe bender and I was trying to replace the tail pipe on my friends explorer when I started to bend the pipe in the bender it just made a big crease in the bottom of the pipe. is there anything I can do or do I just need a diffrent type of metal. I tried two diffrent types of pipe and they both did it and they werent even sharp angles. What should I do?
Thanks,
Zac

[chrism]

I think those benders are made for thicker walled pipe than exhaust pipe. You might try filling the pipe with sand and doing the bend.

[timmirvin]

Originally posted by chrism:
You might try filling the pipe with sand and doing the bend.:D :D Cool idea!!! :cool: :cool:

[TexasJ10]

I have heard of the packed wet sand trick. It makes sense since an exhaust pipe is normally mandrel bent, with the mandrel on the inside and the dies on the outside. Let us know how it turns out.

[Zac]

Well we didn't have any sand to try and my friend needed it done real quick so we just heated the pipe up til it was glowing and then bent it it helped a little but it still made fairly large creases. I read somwhere that along time ago the only way to bend a tube was with sand in it but wouldnt the pipe walls still get big creases in them?
Would the sand make the metal stretch rather than flatten up on top of the bend and crease on the bottom of the bend?

[millertime]

Well I havent used the sand method on a bender but i have bent tube by putting sand in a pipe and corking both ends. Then You heat it up and bend it withought a bender. This seems to work pretty well but use dry sand not wet. Wet sand tends to expand when heated and the corks will pop or the pipe will blow.

[Zac]

Oh did you get any creases?

[TexasJ10]

Zac, Do you have any pics of the finished product? I have a brand new professional made y pipe in my garage that has creases all along the inside radius of the curve. Maybe what you have is actually normal. I think a madrel or sand helps expand the pipe so the creasing is minimal, but I also think that a lot of professially bent pipe has creases as well.

[Wagillac]

Good exhaust bends will not have creases. Most muffler shop benders will crease it some but pipe benders are even worse. To get good bends you need a mandrel bender but thoes are out of reach for even most shops $$$ wise.

[HeepofaJeep]

...i have bent tube by putting sand in a pipe and corking both ends. Where did you get/what did you use for a cork?

[mdill]

For smaller stuff, you can fill the tube with soft wax, cork the end of the
tube pore hot wax in, let cool, bend the tube to shape, heat the tube and melt the wax out.

Mike D.

[jeepguzzi]

The benders used by 99% of the muffler shops are not mandrel benders, they are tubing benders and use dies, not mandrels. A mandrel will maintain the diameter of the tubing throughout the bend. A tubing, or exhaust bender will make the diameter smaller in the bend by kinking or wrinkling the inside diameter of the tube.

If you thought tubing benders were pricey, try pricing a mandrel bender!!!!

[millertime]

you can weld a peice of metal on the end and cut if off when your done or you can shape a peice of wood to fit the pipe and jam it in there.

[millertime]

oh I forgot pack the sand down with the end of a hammer of a wooden dowel. Ive heard of people tack welding in an engine core plug or a "freeze plug". And remember use dry sand if you plan to heat it up after you cork it. You can torch the sand to make it dry as it can be

[Zac]

Will this work in the pipe bender? And if I use sand it wont crease right? It still seems like it would crease.

[jeepguzzi]

Originally posted by Zac:
Will this work in the pipe bender? And if I use sand it wont crease right? It still seems like it would crease.If by crease you mean wrinkle the inside of the bend, then, Yes, it will crease unless you use a mandrel.

[Kaiserjeeps]

I have some expansion plugs from ace hardware. I use them to store radiators with coolant inside them. Prevents dryrot. I also have used them to plug the open axle tubes out at the knuckle when sand blasting or pressure washing an axle housing. Couldn't you use two of these plugs in the piece you are bending? They tighten up with a nut and grab pretty darn tight.
It might work, they come in different sizes....

[Dive 30]

My experience is with bending conduit which is different than exhaust tubing, but, typically I have only used sand in PVC pipe bending to maintain the radius of the pipe for heat bending. With EMT (thin steel conduit similar to exhaust tubing) I have found that most crinkling problems are caused by operator error, unless you have a worn shoe or die. But remember, we mostly hand bend, if you are using a hydraulic bender, this may not apply. When hand bending, your pressure needs to be on the foot of the bender, pushing the shoe or die, not on the lead of the bender, pulling. I hope that helps.

Phil

[TexasJ10]

I just re-read this series of posts and finally picked up that Zac is using a pipe bender, rather than a tubing bender. Packing sand will probably help but the way the pipe bender works verses a tubing bender is different. Dive 30 is right that a tubing bender supports the tubing throughout the bend whereas a pipe bender has a die in the center and two rollers on the outside edge which leaves the pipe unsupported. For thick wall pipe this is ok, but it will kink thin wall tubing. This is discussed briefly at the following site

http://www.lowbucktools.com/benderFAQ.html

[ February 12, 2003, 09:19 PM: Message edited by: TexasJ10 ]