# Tube bender



## MrCrankyface (Feb 9, 2020)

I need a tube bender for a tiny job so figured I'd overbuild it and use it for all sorts of things in the future.
Should be a great opportunity to practice fabricating.

Whipped this up after googling around for inspiration.
The bottom die/mandel/whateveritis will be cut on the lathe or 3D-printed depending on what I'm trying to bend, for copper/aluminium, 3D prints will be plenty strong.
The die in the pic is tiny since I want a small-ish radius for this job, for "normal" jobs they'll be bigger.
With interchangeable dies I should be able to bend square, round tubing and maybe smaller flat bar.



Cutting whatever I have lying around the shop to size.



Of course my bandsaw decided to have a little breakdown so went with this instead.
If you ever use red dykem, remove the mill scale first ... The scribeline was almost impossible to see.


Quite a lot of time spent trying to make this with g-code on my ghetto CNC mill but it's all part of the learning experience. 


"MAIN" will be welded together with the smaller strip above, going to be a challenge to keep the warp down.
SEC used to be those really rusty pieces, did a horrible job flattening these in the mill, my setup was all wrong but now I know what not to do next time.
By being lazy, I made it take tons more time than it would've taken to do it "the right way".


Another half-success/half-fail part, this will be the handle/lever at the top in the first pics.
At least the tube came out alright. 
The side-plates had quite oval circles due to the mill having worn screws and the backlash compensation not being able to compensate enough, trying to fix this I managed to mess the part up even more with the boring head ...
Too high feed and a line of code that I missed that made it move sideways, almost needed a change of underwear afterwards...
It will all be welded together so at least I can hide my mistakes but I'll have to do some tricks to get the tube centered in the oversize holes.


----------



## MrCrankyface (Feb 17, 2020)

Managed to cut all the parts out on the CNC, learning tons doing it.
Last 2 pieces I cut, took 25% of the time of the first single one I did... 
I sanded off and plastered in a ton of toolmarks and other uneven surfaces like where I welded the middle pair etc.



I had a major brainmelt here.
The holes in the handle part(smaller part to the left on pic) are too big, were supposed to be 12mm but for some reason I made them closer to 24..
Ended up drilling the holes up to 26mm since they weren't perfectly circular and then making a 2-part bushing thing.



It all goes together like this and the smaller part will get a longer handle attached to it eventually.


I'm hoping this will work ...
The smaller pipe/bushing is a slight press-fit into the lever part, this should hopefully keep the thicker bushing locked into place and make sure stuff doesn't fall apart.
If I can't get a good enough press-fit I will probably end up using some kind of loctite.
Once fully pressed, it will be flush with the surface.


----------



## Lo-Fi (Feb 17, 2020)

Fantastic project!


----------



## Cheeseking (Feb 17, 2020)

Cool. interesting variation on a Hossfeld type bender.


----------



## Ulma Doctor (Feb 17, 2020)

very nice!!! 
i like the heavy duty construction


----------



## MrCrankyface (Feb 18, 2020)

Thanks everyone!

Managed to finish off the lever/"saw" today.
I wanted the handle to be easily removeable so it has a loose slidefit.
Also pressed a collar onto the handle(the part that goes off-screen) to give it a good stop.



I wanted to try something so I cut the tube up and hammered it into oblivion to make the end close up.(the one that had a blue strip in previous pic).



Finally managed to get a good-ish weld on this thick stuff, probably my best weld so far!
You can also clearly see how I missed my tolerances when lathing that smaller piece.  



Finished handle/lever/rack assembly!
I've hung it up for paint now and applying some zinc before painting them.


----------



## MrCrankyface (Feb 22, 2020)

I think I have all the parts now. The two frames are assembled and the rack/handle is disassembled for paint.
Needless to say, I had a few cans of red over from a previous project ... 

Just need to wait for the paint to dry completely then I should be ready for final assembly and to give it a try!


----------



## MrCrankyface (Feb 24, 2020)

I gave it a first test-run during the weekend and at the same time realized I forgot to include any way to mount the thing ... 
	

	
	
		
		

		
			




Had to clamp it across two bolt heads since I didn't want to mess up the paint the first I did.
First tests resulted in quite deformed pipes.

Tracked down the culprit to the mandrel, the sideways bent outwards under the force of the pipe, allowing it to widen and flatten.
Reprinted a much wider one which also extends out forward more for easier locking down of whatever you're bending.



Also added this mount so I can hold it in the vice, I could replace this with something that lets me bolt it to the worktable as well for bending thicker pieces.



Here you can see the lock tab and new hinge pivot pin.
I suspect the lock tab is another possibly issue, sometimes you can see the pipe slipping and it's usually at that point it flattens the bend.
I have another design ready but haven't had time to make it.
Being a bit careful and not bending above 70* gives you pretty good bends!


For pipes these smalls you can almost bend it with 1 hand on the arm itself. Using the handle and extension, one finger is enough.


----------



## Dhal22 (Feb 24, 2020)

Nice work!


----------



## MrCrankyface (Feb 27, 2020)

Thanks!

Work continues on trying to improve the bend result..
This is how the pipe gets held when bending.



And this is what happens when you try to bend too much. The pipe starts slipping in the holder and you end up crushing it instead.
Hopefully fixing this will result in near-perfect bends.



Added a bunch of sandpaper and squeezed it real tight ...
Aaaaand even a 180* looks pretty mint! You can see it's more flat towards the end of the bend, that's because my plastic die split...



So here's my next step ... Solid aluminium.


----------



## MrCrankyface (Mar 1, 2020)

Finally found a combo that works! Aluminium die, steel holders and generally a tight fit.




Used a small piece of pipe and rough sanding paste to get that second die in near-perfect shape and colinearity.
Applied some grease before trying to draw the pipe.



Here's the two dies.
Unfortunately the diameter was too small to get my different positioning holes drilled into(they'd intersect the pipe form) but this small diameter is easy enough to bend by hand so it only really needs 1 position.



So this finally let me do the last bends and finish my air system. Time to clean up I guess.


----------

