Thread: Home made hydraulic tube bender

Hi guys,

This is something I have been meaning to post for a while. Its my biggest project to date and one which required the use of the holy trinity of workshop tools - A mill, a lathe and a welder.

I based this design off other things I had seen around the web. It was built and rebuilt a number of times before I had the final product. Testing revealed deficiencies in just about every part I made except the main pin which meant a significant amount of wasted time remaking parts (I prefer to think of it as time spent learning). Anyway, in the end I have a hydraulic tube bender that works very well and which only owes me $200 - $250...a fraction of what you can buy them for. Following are some explanations for the attached photos.

Photo 1) This is a photo of the very crude (but effective) cutter that I made to cut the profile in the die. The die itself was a piece of 250mm by 40mm steel that I bought. In hindsight, I should have got 250mm by 50mm or even 60mm to give me extra steel to play with. After I cleaned up the piece and cut a 32mm profile in it there wasnt much wall thickness on one side.

Photo 2) progress on the die

Photo 3) another shot of my crude cutter. It just uses some HSS and pivots on a bolt. Looks sh!te but worked flawlessly.

Photo 4) The profile in the die is complete. The die is for 1.25 inch tubing, and the bend radius is just over 4 inches. This die pretty much maxed out my lathes capacity.

Photo 5) This is me working on the main pin. This goes through the center of the die and cops a lot of force - so it had to be beefy. Its made from 52mm free cutting steel. The main diameter is 30mm. I am taking a big cut in this photo and the finish I was getting was awesome. Check out the colour of the swarf!

Photo 6) This is the lathe work complete on the main pin. As I crept up on the 30mm diameter the finish deteriorated with the small cuts I was taking. It was at this point that I realised my lathe doesnt cut true as there is a measureable difference in the diameter of this pin along its length.

Photo 7) Finished pin with a knurled nut to retain it in the bender. In practice this nut doesnt achieve much as you can bend without it and the pin doesnt move at all.

Photo 8) Die complete with pin in place. I did a lot of mill work to get the die looking like that...alas..didnt take photos. The final die had lots more work on it too, i.e I had to drill additional holes for the jack retaining pin to allow me to do bends up to 90 degrees. Also, in this pic the lone jack retaining pin is only 20mm...this wasnt strong enough (pin was bending) so I bored out to 25mm for the final die.

Photo 9) This is the foot/bracket thing that connects the hydraulic jack to the die. I.e the jack pushes on this and this pushes on the die bending the tube. This is the 6mm version - it buckled during testing. Had to beef it up for the final product.

Photo 10 - 13) This is the final product. Hopefully these pics give you an idea of how it works. Basically, you pump the jack which forces the foot down onto the die. As the foot is pinned to the die - this forces the die to rotate. The tube to be bent is clamped to the die, which means it is bend around the die as you pump the jack. You can get about 25 degrees out of it until the jacks stroke maxes out and you need to compress the jack and insert the foot into the next hole in the die. In photo 12 you can see the 'follower'. This is the part that follows the bottom of the tube as it goes through the die ensuring the tube doesnt distort.

Photo 14) This is an example of a couple of bends I made. 71.5 degrees in 1.25 by .120 (3mm) 1020 mild steel. These are the lower frame rails for a hard tail custom motorbike frame. Thats my main project and the reason I built this bender. The tube crushed about 1mm in the middle of the bend, but with tweaking of the follower I should be able to reduce that (test bends made on a shoddy temporary follower were only crushing about .4mm). The 16 tonne jack bends this steel it like its butter. As you can see, there is no wrinking in the bend which is excellent as wrinkling is very undesireable. There is a small amount of crushing though, which is manageable...as I said before I hope to improve this crushing with further work to the die.

Any questions please fire away!

Brendan

Looks great Brendan,
You're right, thats one ugly radius cutters you have there, but it sure works
Are you sure its not just that your tail stock is offset that the lathe is cutting a taper?

How did you machine the follower die?

Stuart

Nice job. I hope to be able to undertake a project like that some day

Hi Brendan,

Congratulations on a great job, 16 tonnes should make short work of bending pipe all your pipe from now on.

That profile cutter is a classic. The bends in the final picture look good.

Nice work.

Regards
Ray

Hi Brendan, great right up.
I remember you talking about this a while back, nice job and very inventive with the compact radius turner..
If you keep you eyes out, I have seen dual stage jacks around which would save you moving pins if it becomes a bother.
Yours sounds and looks like it works great , the supercheap one I have crushes the tube all the time, which makes it not worth using.

I agree with Stuart about your tail stock is probably out if it's turning a taper.

Dave

Hi guys,

Thanks for the comments.

yeah..the tailstock is probably the cause of my problems. I put a post up here somewhere and got lots of help on how to fix it. Its just a matter of doing it now.

Re the follower - I centered a piece of 40mm x 40mm x 125mm steel in the 4 jaw and then bored down the middle to 32mm. Then I took this out, put it on my horizontal mill and used a thin Hss saw to slice it down its length, giving me two semi circles of 125mm each. These were placed end to end and welded to give me an overall length of 250mm (which is what is required for 90 degree bends).

The first incarnation of this follower was a piece of railway line that was mounted in the vice on my horizontal mill. I then put in my collet chuck, and mounted a 1.25inch by 10inch end mill that I have. I then used x axis to feed the sleeper into the end mill, raising the y axis 1 or 2mm at a time until I had about 1/3rd of a circle in the 250mm long piece of rail. It was rough, and the flex in the end mill meant the profile was deeper at the start than the end. Funnily enough though, this shoddy follower gave me a much better bend than the planned and accurate job I made for the final bender.

Re the radius cutter - yeah it wont win any beauty contests but man can it cut. I think the HSS bit used is 3/16 and I only had to sharpen it a couple of times to do the whole job. I think for memory I did the job at 90rpm. The bit was sharped to be symmetrical and pointed, almost like a threading bit. A stainless tube I have slides over the arm to give me leverage and the cutter is held in my QCTP. I would take a cut then wind in the x axis and take another. This was the only way I could machine a piece that big on my lathe, as the various sturdy plans for ball and radius cutters that you see floating around would foul the job on my lathe.

Real nice job and your radius tool is spot on. Thats how i would have made it...Bob

Cheers Bob.

I forgot to mention how it operates. In photo 10 you can see where the tube is clamped at the front of the die. normally, in operation there would be a length of tube protuding from here. All you I need to do to accurately bend is to put a digital magnetic protractor on the protuding tube and start pumping the jack. You can watch the angle of the bend increase with each pump of the handle. For memory a full stroke of the jack handle will give you about a degree. It is easy enough to bend accurately to within the resolution of the protractor (.1 of a degree). The only thing that needs to be taken into account is the spring of the steel. in the case of a 25 degree bend, you lose a couple of degrees to spring. So if I am aiming for 25, I will bend until the protractor reads 27 and the spring will take it back down to 25. In the case of my 71.5 degree bends, I was losing about 6 degrees to spring.


This is the protractor that I use.

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Brendan

HI,
Thats a Great Job Brendan WELL DONE. The Die looks Great, a shame though on the Wall being a bit thin on one side.

Good work son. I could never take on such a project.....
I bet it makes you feel good.

Looks good the only thing i can see which you may have trouble with is the die. You may have some trouble with the pipe kinking on tighter bends as usually the pipe doesnt sit right down in the die like yours it ends up being tight on the pipe after you have bent it and stops the pipe from kinking.

Hey Steran, Cheers. In the end I put a 3mm plate on the thin walled side to beef it up a bit. I drilled a stack of holes through the plate and welded it to the the die. I then welding up all the exposed edges too. It looks a lot better now.

Hey Sterob - Yes you could! With the right tools at home and a friendly forum like this you can get pretty much anything done. Throw in a few lessons at tafe and a few hours watching vids on youtube and your imagination will be running riot.

Old Fella - I was really worried about kinking but so far it hasnt, and I have bent up to 90 degres. There is a guy in WA who built a similar one and I read his stuff in depth whilst building mine. He uses oil which he thinks prevents kinking...I do this too, but it bends fine dry. I figure the oil cant hurt though.

Brendan, fantastic job - looks like a nice piece of gear. I was curious though - in pic 13, the part when the legs from the jack push on the rotating die - looks like the legs could slip off under pressure??

I know some people pack their tubes with sand to avoid ripples/crushing, but it looks like yours works no problem at all.

So what are you planning to make now that you can bend tube nicely?

Cheers

- Mick

Hi Mick,

Good pickup. The pin that pins the legs to the die was the same one I used when the legs were only 6mm plate (now they are 10mm). Its only about 60mm long so with 40mm of die and 2 10mm legs there is no overhang. I was worried about it popping out too, but in use it doesnt move at all. For the sake of 3 inches of steel and 10mins of my time I probably should make a proper one.

The project it was built for is a custom motorbike frame - a traditional hard tailed 'bobber'. Photo 14 is of the two lower frame rails. The frame is not in its natural position though, the tubes extending to to the left on the photo are the bottom rails, i.e the bit that goes under the motor...and the tube to the right is the upright portion of the frame that reaches up to the necktube - where your forks attach.

I'll put up photos of the frame in a seperate thread as it comes along. Im waiting on more tube to arrive from performance metals, which im anticipating today or tomorrow.

Australian Chopper ! Cool - keep us posted Brendan. Cheers - Mick