A tube bender saga

[Mcgyver]

I made this a few years, ago but used it today and have never taken photos of it so thought you guys might like to see it.

occasionally when making models, one has to bend copper tubing. the typical tube bender, while successful in creating a bend, is not up to the task for modeling as 1) it won't work to a small enough radius and/or 2) distorts the shape of tubing around the curve - ie not a smooth transition from curve to straight on both the inside and outside curves. Thus began a bunch of experiments and reading on to produce a decent bend in a tube.

What I came up with has two unique (well they were to me anyway) features. 1) the outside die, rather than being a round die like the inner is straight. 2) the outside, straight, die, gets tightly pressed against the inner die, sandwiching the copper tube between them. This done via an eccentric axle. If you look in the pic, you’ll see the straight die, then a cylindrical spacer. It's this cylindrical spacer that is on an eccentric shaft.



Here a bend is being set up. The tube clamp shows a larger allen key setting the orientation of the clamp along a tee slot, while the smaller one clamps the tube itself. I made slit spacers for different sized tubing. In the main pivt, about the round die, there are spacers such that it is firmly bolted to the base, yet free rotate.



here's a shot after completing the first and second bends. the tube was annealed for these bends

[Mcgyver]

(stupid image limitation)

here's a close up showing the fairly decent shape that is maintained. ideally the bend looks like 1/4 of a torus without kinks or ploughed-up leading edge to the bend.



of course, if you're going to make a tube bender, you're going to do so for all sizes of tubes and radii. Should I ever commit a heinous crime, I consider this important work towards my insanity defense. It handles tubing from 1/8 to 3/8 by 16th’s



after cutting to length and some emery and polish work, here's the finished product. It’s sitting on the block to which it will one day be attached. Imo it turned our well, its a .5" centre radius bend in a 5/16 tubing. Still, the Stuart plans (this is for a triple expansion) calls for a 5/16 centre line bend, the accomplishment of which still eludes me, even with this rig. perhaps filling with cerro or something.

[Tony]

holy smokes, mcgyver, thats some pro looking work there.. good job.
some of those surfaces look hardened?

-tony

[Ken_Shea]

That is a very neat set up McGyver, nice job.

Looks very complete

[Carld]

Very nice set of benders. Someone in the future is going to think they have a factory made set.

[Rich Carlstedt]

Very Nice WOrk !
They have the straight sections in "Large" Commercial benders
They are called "Shoes"
A shop my company had doing work for us used them when bending
our pipes. They could bend a 3 1/4" Stainless Pipe with a 7/8" bore and get a 6 inch radius ( or 7 5/8" C/L) for us.
Obviousely when you do something like that, You have to pay the vendor for making the custom shoes and rollers.
Rich

[h12721]

A tube bender saga

Mcgyver,
(this is for a triple expansion) calls for a 5/16 centre line bend, )

Check your print, it is 4 5/16 CRS.
Hilmar

[dp]

Lots of eye-pleasing workmanship detail work there. Very nice and just a little bit, no, a lot old school. Well done.

[Buckshot]

........That is fabulous work. It shows a lot of attention to detail and the final finish is just great. Looks just like the kind of old time craftsmanship that's very hard to find these days. Except by dedicated individuals :-)

Rick

[Evan]

Excellent job. I'll be posting pics of my sort-of-like-a-Hossfeld bender I recently built when I make a few more dies and have some work from it to show.

[abn]

Consistently impressive, your work looks great!

[Mcgyver]

thanks very much guys, appreciate the kind remarks. around here its just another hunk of metal dad spent hours messing with so its good to show it to people who get it. nothing is hardened, figured its low duty cycle and bending copper. I will probably use casenit on some parts, ie the top 3/8 hex on the pivot is starting to get dinged up. The finish is just the wipe on blue done to help fight rust.

Hilmar, that tube shown is 4 5/16, what i was referring to was the print requirement that the bend be to a 5/16 radius along the centre of the tube - was i missing something?

[laddy]

Phenominal, I have settled with the ugly crude bends over a dowel, Yours looks fantastic!!!

[Your Old Dog]

Nicely done Mac!

[h12721]

No You don't. I was. Sorry.

Hilmar