tube bending experts

[johnakay]

manage to make a former for bending 22mm ERW tubing.
I had a 20mm former and grinded that out etc and a linisher to get the curve.
its roughly 3".1/4 -3.5" radius on a 5" former.
it wont have it.
I think the radius is to small to get an even bend.
that's probably why Hilmor only do a 8" former or there about.
what do you experts think?

 

[Mikes]

What wall thickness? if it's thin, the only way of doing it is with a mandrel bender or by heating the pipe with oxy/acetylene and pulling it around a former manually. It's hard work but you can get some very neat bends this way with practice. Alternatively, is it something that you could use 1/2" BS1387 mild steel pipe (typical commercial heating pipework) which has an o.d. of 21.70 mm . This could be pulled using a hydraulic bender and typically a former for this size has a good tight radius. You could even use this pipe and weld bends to it.

 

[addjunkie]

I have a el32 conduit hilmor bender, does 1inch tube no bother at all but from memory its 41/2 inch clr. The standard conduit dies have a deep grove to support the sidewall during the bend. I have other dies too, slightly smaller clr for 20 tube.

 

[Agroshield]

When you mention a 20mm former, that makes me think you are using a conduit bender, with just a roller on the top of it.

Maybe consider converting it to, or buying a former from, the type of bender used for copper plumbing pipe. In that, the roller presses on the outer former, which is kinder to the pipe.

You could also try filling it with well-packed kiln-dried sand and seeing if that makes any difference.

 

[outofthefire]

Fill it with kiln dried silver and warm it up if necessary it'll bend without kinking.

 

[johnakay]

this is my current bender see pics.it is based on a hilmor.
former is specially made to get the correct bend. hilmor isn't quite right.
20 mm former was grinded out . it should bend the 22mm x 1.5mm wall.
but I think its on a sharp side.
I dont want nor am I going to start packing the tubing with sand etc.
everything is bent by hand.
I can get 19mm x 1.5mm bent easily enough so maybe 22 is asking to much on such a small radius.

 

[Agroshield]

If it is ERW tube, have you experimented with the position of the seam? Inside or outside of the bend might make the difference. From your photo, it looks like a concave roller held by the yellow pin. How closely does it match the OD of the tube? Where does it press on the tube relative to where the inside of the bend touches the inner former? A good clamp on the inside of the block that retains the end of the tube, to stop it moving laterally might help.

Have a look at this:

https://pro-tools.com/blogs/protool...to-the-center-of-the-centerline-radius-debate

(Also, for backup info: http://files.engineering.com/download.aspx?folder=329c633c-d992-46da-9cc2-ed01a5e2e8ee&file=tube.pdf )

and work out your wall factor and 'D'. See where it lies on the graph and then you will have an idea of the direction in which to proceed.

 

[Shox Dr]

Post a picture of the failed bend

 

[johnakay]

see picture of former for size roughly.
on the 1st picture of the failed bend you can see where it failed on the inside and slightly squared off on the outside.
the other was done on the hilmor former good but radius is to big.

 

[Shox Dr]

I dont think you can fault that considering its ERW.

 

[johnakay]

I dont have a problem with a Hilmor former due to its larger size.
across it measure 147 mm(inside)the home made one is about 90 mm. so theres a big difference .
bought a 5.5" aluminium round bar last week.
the biggest I'll be able to machine out will be 110mm.
do you guys think this will do?
I know I'm asking a million dollar question.

 

[Shox Dr]

You are asking too much of erw. 90mm CLR is very small. Better off using CDS

 

[johnakay]

thats why I'm asking on here.

what is CDS?

 

[Richiew]

Cold drawn seamless (tube)

 

[addjunkie]

Also called CFS3

 

[Shox Dr]

thats why I'm asking on here.

what is CDS?

There are two types in common supply. Note; also called hydraulic tube.

this is one of them https://www.hublebas.co.uk/products/cold-drawn-seamless-hydraulic-tube-cfs-nbk/

difference been one can take bends closer together. I’ve used the lesser without problems

 

[johnakay]

after much thoughts. I think I know where a I'm going wrong.
in the picture below that is where I start to bend on the outer roller.
so its not getting the support at the beginning ,that's probably why its not working.
it should get the support at start of the bend.
I'm only doing a 90 degree bend so it should work,I'll have a look tomorrow.