Bending tube

[Graham_Wright]

I have just - as in at the weekend - succeeded in bending 1 inch ss316 tube in a bender i made out of plywood.
Smooth bends without kinking. No Sand or forming springs and absolutely minimal flattening of the tube.
I am so pleased with the result!
Having failed with a hydraulic bender due to wrong formers , I was inspired by the you tube video here.

http://www.youtube.com/watch?v=lcTIDlDevog

Pity he doesn't show it in action! A Youtube link to a similar device does though. The technique seems to work as the tube is pulled by the friction attachment at the end thus stretching the tube not squeezing it.

I made mine in a similar fashion to this.
I believe the secret is to get the profile of the groove just right ie a perfect 12.7 mm radius.
I made my big forming wheel/mandrel a radius of 150mm and i made two smaller wheels to feed in, so larger radius will be easy.

Let me know if you would like more detail.
Good luck.

My bending device was a failure as it was just compressing. I jibbed at the thought of turning a 20" diameter wheel because I was thinking metal. One of my lathes can swing 31" so a plywood solution should be straightforward
I have just fallen out with routers as I bought a "bargain" B&Q router table that is driving me to insanity.

For bends of less than 360°, a whole circle should not be necessary if it actually saves anything.

 

[Lakesailor]

For heaven's sake get in your car and drive 10.5 miles and pay a man to do it properly. http://www.warren-engineering.co.uk/

 

[Graham_Wright]

For heaven's sake get in your car and drive 10.5 miles and pay a man to do it properly. http://www.warren-engineering.co.uk/

Great - thanks very much. I've tried three locals - two couldn't and one tried and failed.

I'll give them a ring. I don't mind paying as my time is precious.

I've just spoken to them and they can't do it. The problem boils down to mandrel sizes and mandrels for ring benders are not simple "pulleys".

However, - thanks for the steer.

 

[Lakesailor]

....and find out how his machine works. His bends look perfect.

 

[John the kiwi]

Seems like there are a lot of tooth sucking theoreticians on here who have never tried this but have plenty of opinions. Normal Forum I suppose.

I tried a hydraulic bender but the mandrels were all wrong .
I tried making a plywood mandrel but couldn't get it to work without kinking even with SAND PACKED in the tube.

So i made the device pictured and did my bends without sand or ice or inserts or heat.

View attachment 43341View attachment 43342View attachment 43343View attachment 43344View attachment 43345
A lathe would have made the job much easier, but I did my wheels with a jig saw and radius arm - each wheel is two halves of 18 mm ply.
I screwed them together and sanded the imperfections before separating and doing half of the groove in each piece on a routing table.


The large wheel doesn't need to be full circle and is easier if it isn't as i was able to detach the retaining loop and rotate the wheel to release the whole bend.
Hardest part was actually mounting the thing rigidly enough in the middle of the workshop to allow swinging room for the tube.
I did use a longer bar inside the RHS and it was physically easy to bend.
Hope this helps someone.

Cheers


PS on looking at the photos, the flash seems to accentuate the flattening. Not saying there is no flattening, just that it is not as pronounced as it may appear.
On my next effort i may sand pack the tube as well.

 

[Graham_Wright]

Seems like there are a lot of tooth sucking theoreticians on here who have never tried this but have plenty of opinions. Normal Forum I suppose.

I tried a hydraulic bender but the mandrels were all wrong .
I tried making a plywood mandrel but couldn't get it to work without kinking even with SAND PACKED in the tube.

So i made the device pictured and did my bends without sand or ice or inserts or heat.

View attachment 43341View attachment 43342View attachment 43343View attachment 43344View attachment 43345
A lathe would have made the job much easier, but I did my wheels with a jig saw and radius arm - each wheel is two halves of 18 mm ply.
I screwed them together and sanded the imperfections before separating and doing half of the groove in each piece on a routing table.

PS on looking at the photos, the flash seems to accentuate the flattening. Not saying there is no flattening, just that it is not as pronounced as it may appear.
On my next effort i may sand pack the tube as well.

The large wheel doesn't need to be full circle and is easier if it isn't as i was able to detach the retaining loop and rotate the wheel to release the whole bend.
Hardest part was actually mounting the thing rigidly enough in the middle of the workshop to allow swinging room for the tube.
I did use a longer bar inside the RHS and it was physically easy to bend.
Hope this helps someone.

Cheers

I anticipate the someone will be me!