Simple way to bend 10mmØ x 1mm stainless tube

I need to bend 10mm x 1mm thick stainless tube multiple times like a spring for my big generator about 50mm diameter coils.

The model 0.25" x 0.028" I had no problem over a wood former by hand to about 1.5" diameter coils with no kinking.

Without buying a tube bender or spending a great deal of time making a bender any simple ways of doing it.

The tube is 6 metres long to start with.

Most of the lower priced 10mm tube benders are for copper.

It's a bit tight but try a spring making company. There used to be loads of little companies doing it, not sure nowadays

I've heard people stuffing the pipe with salt or sand to prevent kinking then wrapping around a cylinder.

Do you need the entire 6m or can you waste some on experiment?

https://youtu.be/EU9OKkgi6Jg

That is a tight diameter. We used to use CEROBEND which is a low melting point metal to fill the tubes prior to bending. For larger tubes 1" and upwards we used a hard RESIN similar to this.

I don't know how, but your tubes need to be annealed - but you know this.

Bob

I have a couple of Hilmor K1a bench top pipe benders, which for a 3/8" pipe will bend about a 1" internal radius, by the time I've spiralled it out for form a continuous spring shape, it had expanded to about 3" diameter OD
I only tried it out on some 10mm soft aluminium air pipe though.
If you know anyone passing through Buxton on their way to your house, I could always loan you one to try out.

Whilst I appreciate the desire to complete the job in a home workshop, I can't imagine that a 6m length of pipe comes cheap to have multiple attempts, and wonder if it might be worth approaching a commercial outfit such as White Cross Ring, who aren't that far from you.
https://whitecrossring.co.uk/services/tube-bending/
I've never had contact with them myself, just the result of an internet search.

Bill

How about making a former to be driven by the lathe, in back gear? a half round guide block in the tool holder would help control the winding as the tube is pulled onto the former. Same technique as a spring winding setup, a powered version of your previous model coil windings, just powered by the lathe. Just food for thought.

Before pipe-benders were invented that was how it was done, but skilled work. The tighter the bend, the harder it gets.

The trick is to support the pipe internally by stuffing it, or by bending it with and around fitting shaped rollers.

Cerobend is more supportive than salt or sand because it's incompressible. Water in a completely sealed pipe might work, but the seal would have to be strong.

I tried sand in 15mm copper pipe once: didn't go well. A bought bending spring worked better, but the result was adequate rather than well done. I didn't practice.

Dave

+1 for Cerobend, but stainless tube is quite stiff, and it will work harden so it will need considerable force and a bit of an over-bend. I had a friend who bent car exhausts commercially using the hard resin, but it was very labour intensive (and smelly).

Marcus

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It might also be a little pricey for the job that Windy has in mind

MichaelG.

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https://www.mkmetals.co.uk/product/cerrobend-alloywoods-metal-lmp3-mp-70deg-kg/

Edited By Michael Gilligan on 23/07/2022 21:59:37

Not so pricey here ?? CERROBEND

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Yeah, but …

The density of Wood’s Metal is commonly given as 9.7 gm/cc

and the internal volume of Windy’s tube, in nice convenient cc

= pi x 0.8 x 600

So, even at the super-low price for that ebay ‘remoulded at home’ Cerrobend

MichaelG.

Edited By Michael Gilligan on 24/07/2022 08:34:34

Would lead possibly be a suitable alternative to the Cerrobend in this instance? Higfher temperatures required, obviously, but maybe kill two birds with the annealing process?

Rob

Where did the 0.8 come from? Shouldn't it be 0.16? Total volume = pi x 0.16 x 600 = 301.6cc = 2925.5gm

Might be a bit misleading it was the model tube 0.25" tube that was bent to 1.5" diameter.

The 10mmØ x 1mm thick will be bent to a 3" or 4" internal diameter.

Am thinking the scrap material box will have to be looked at and make a suitable former etc. for a bench tube bender.

Hi, well you can use 0.8. pi x0.8 sq /4x600= 301.59cc

Regards Nick.

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I think not, Gary

10mm tube with 1mm wall thickness = 8mm internal diameter

Convert to cm

MichaelG.

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Oops … just realised 

pi x d is the circumference not the area

… it was rather early when I posted that.

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Edit: __ at the ebay price that’s not even a hundred quid’s worth 

Edited By Michael Gilligan on 24/07/2022 14:44:59

A response to Grindstone Cowboy's idea about 'killing two birds with the annealing process'. Does this mean annealing the steel and the lead, I wonder?

Something in my memory reminds me that the annealing temperature for lead is below normal room temperature, so the lead would remain soft after the bending. (So, only one 'bird' to kill). If I have a reference here to remind me I cannot imagine which pile it will be in. Am I making any sense, please?

Cheers, Tim

If you have a look at the Hilmor bender I linked to earlier, it's fairly obvious how it works, though there is an additional missing part; this is the outside mandrel, which in this case would be a 10mm square bar about 150mm long, with a 5mm radius groove down the centre of it.
The main half round yellow mandrel with the 10mm groove in it, could be made slightly differently. Rather than just a concentric groove, how about having one at a slight angle?
It could still be turned as a conventional concentric groove in the lathe, but the two ends milled off parallel, but at an angle to the axis.
You are only using half a circle's diameter for the bending, so this would then set up the angle for the tube to spiral upwards.

Bill

Bill

Hi Tim

Never even considered annealing the lead, I was thinkink of maybe filling the tube with lead shot, and then heating it above the melting point (of the lead) in order to fill it completely. Obviously the lower end would be plugged and heating would start at the bottom, ultimately resulting in a "solid" rod which could then be formed as required. Maybe the heat required to melt the lead could also serve to anneal the tube - but no idea of what temperatures would be involved.

Possibly the lead would deform too much to support the tube without kinking - I can imagine it could be awkward getting all the lead out afterwards too.

Best regards,

Rob

Lead melts at 330 C. You need to be a lot hotter than that to anneal stainless.