Bending 7/8" 4130

[anon.]

Hi all,

I have an idea that I've been wanting to try for a while, and the whole thing centers around pulling a *VERY* tight radius bend with 7/8" 4130. I'm wondering if anyone on the forum has experience working w/ tight radius bends on 7/8" tubing, and if so any tips/tricks/equipment advice would be much appreciated.

I'm guessing that the diacro #3 is the necessary size needed... is there a less expensive alternative to this piece? Is cerrobend or sand filling going to be necessary?

Thanks
Michael
chi il

[Clockwork]

What radius are you looking for? I suspect you won't be able to do it yourself. I get these 1.25" x .058" 4130 tubes bent to a 3" clr using a draw bender. They (Flour City Bending Inc.) list tooling for 1.125", 2.00", 2.25", 2.38", 3.50", that's assuming they have the correct internal mandrel, though.

LDs | Flickr - Photo Sharing!

-Joel

[anon.]

Thanks for the link - I'll give them a call.

[FrankTheWelder]

These are mandrel bent 7/8X.035" 4130N. It is expensive to bend like this in small quantities and very challenging. There are two rads in these. DOM 1020 is easier. I have three or four radius in 7/8" and mandrels for .035, .049, .058.

http://www.flickr.com/photos/frankthewelder/5258820093/

Here is the 2" die in action bending .065" wall 2" aluminum. This machine is powered by a pneumatic motor that can produce 400 ft/lbs of torque

http://www.flickr.com/photos/frankthewelder/4494187399/

[steve garro]

Here is the 2" die in action bending .065" wall 2" aluminum. This machine is powered by a pneumatic motor that can produce 400 ft/lbs of torque

MVI_2984 | Flickr - Photo Sharing!

I used to run one of those very much like that at work that had an expander/reducer on one end, on Al. as well - where is the big-ass dead blow that sits on top?
- Garro.

[anon.]

That is a serious piece of machinery.

[FrankTheWelder]

That is a serious piece of machinery.

Here is the most serious bender in the house. I would like to find a smaller version of this one.

29 350 | Flickr - Photo Sharing!

[jon_norstog]

I bend 7/8" x .035 chrome moly stays for all my BMX bikes and some of the others as well. My ProTools Hossfelt-style bender will do a 4" radius to about 16 degrees before the tube starts to wrinkle. I can do a little more if I anneal the tube. I used to heat-bend for tighter radius, but a few years ago I had Chapman Industries in LA bend me up 100 sets of stays with a 3" radius bend at one end. It was cheaper than Taiwan! And they used milspect tubing in stead of mystery metal.

I can put the second bend into my stays on my own bender so I can use the same basic tube on 26" BMX frames as well as my 4-cross bike and a few others. The 20" and 24" bikes have easier bends so I do thos all in-house.

jn