Pipe bending

[John MCParticipant @johnmc39344]

I have the occasional need to bend thin walled steel tube, diameters range from 19mm (3/4&quot to 50mm (2&quot. I have been looking to buy a suitable pipe bender.

Plenty of the plumbers type that use a former to suit the diameter of the pipe. This could get expensive, a different former for each diameter, especially as some diameters I need to bend are not "standard" sizes.

Does anyone know of what could be called a universal pipe bender? Something that has an adjustment to cover a range of diameters rather than changing formers for each diameter.

John

[John MCParticipant @johnmc39344]

[Nigel BennettParticipant @nigelbennett69913]

Hmmmm…. If you think up a way of making a device that can easily adjust to different tube diameters like that, the world would beat a path to your door! And if you can adjust the bend radius as well…

You need really good support in my experience to avoid kinking the pipe, and that can only be achieved as far as I am aware by having bespoke formers that cuddle the tube really closely.

I cannot conceive of any method of doing what you want, and even if it were possible, I doubt if you or anybody other than Elon Musk could afford one.

[EmgeeParticipant @emgee]

John

I would guess that bending thin walled steel tube needs the support of good formers to prevent rippling and/or squashing of the tube, I found bending 25mm diameter steel electrical conduit in a 1" former results in a slightly oval tube.

Emgee

[Michael GilliganParticipant @michaelgilligan61133]

Good point, well-made, Nigel

I guess this is where Cerrobend and the like come to the fore

**LINK**

https://uk.metaconceptgroupe.com/produits/cerro-alloys/

MichaelG.

[Martin ConnellyParticipant @martinconnelly55370]

Sorry to say that I think the only cheap option would be to get someone with a pipe bending machine to do it for you. Even then if you want to bend a size they do not have formers for they would charge you the cost of getting suitable formers.

You do not say what you mean by thin wall but as the wall gets thinner you have to start supporting the inside of the tube and as the radius gets smaller you need to start thinking about boost on the bender Y axis and wiper dies. You have also not stated what ovality or wall thinning you could live with. This is controlled by the pressure and bend dies.

I bought an Addison DB89 for work in 1993 to bend pipe from 1/2" OD to 2"NB and even using tooling from the machine it was replacing it cost £140k. Each set of tooling to suit a new diameter cost about £2k. Mandrels to cover different wall thicknesses cost up to £1k each.

I made some 1/4" tooling for it with aluminium bronze for the bend die, this is the first test of the tooling.

These are images from the cardboard computer for calculating what tooling you need for different wall thicknesses and bend radii.

Martin C

[Paul LousickParticipant @paullousick59116]

There are lots of DIY pipe benders on Youtube and internet which are simple to make. Tube and pipe can also be bent by packing sand in the tube and plugging the ends. Then heat with a blowtorch to bend. Make sure that the sand is completely dry or any moisture will turn to steam when heated.

Paulthe

[Bo’sunParticipant @bosun58570]

Posted by Paul Lousick on 13/02/2021 10:24:19:

There are lots of DIY pipe benders on Youtube and internet which are simple to make. Tube and pipe can also be bent by packing sand in the tube and plugging the ends. Then heat with a blowtorch to bend. Make sure that the sand is completely dry or any moisture will turn to steam when heated.

Paulthe

Steam driven blowpipe. Now there's an idea.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Martin Connelly on 13/02/2021 09:32:57:

[…]

I bought an Addison DB89 for work in 1993 to bend pipe from 1/2" OD to 2"NB and even using tooling from the machine it was replacing it cost £140k. Each set of tooling to suit a new diameter cost about £2k. Mandrels to cover different wall thicknesses cost up to £1k each.

[…]

.

Fascinating stuff, Martin

… and interesting to note that they are still apparently doing good business

**LINK** : https://www.addisonforming.co.uk

presumably therefore, the machines must be good VfM

MichaelG.

[noel shelleyParticipant @noelshelley55608]

This is an interesting one ! If you checkout pipe sizes for standard steel tubes they will be qoted as NOMINAL bore, because whilst you can have varieing wall thickness the O/D will be the same, so that you can have one size of former for a given size, eg 1 1/2" nom bore will be 48.3mm & 3 wall thicknesses. As the OP has stated that he wishes to bend thin wall pipe a ORDINARY pipe bender is unlikely to be of much help since the bend raudius is fixed and the thinner the wall the more gentle the radius has to be. For ERW tube the size is the O/D and many are imperial, expessed in metric. Back in the 70s there was a shortage of copper pipe for plumbing and all that was available was a much thinner wall. It proved to impossible to bend using a normal pipe bender, so fittings had to be used. As Nigel has said IF you come up with a design that works , I'll have one !

Back to the real world, Packing with sand and heating is worth a try. Lead or woods metal might work, but the thinner the wall the more inclined to crease or wrinckle it will be. A bending spring is unlikely to work,and for steel you will need steel formers, if you can find them to suit the O/D you want. Rothenberger make them but they are pricey, or you could make your own, if you have a machine large enough. To work cold you will need a hydraulic machine for all but the smaller sizes. I have a machine that will work with pipe to BS 1387 up tp 2" that if your near me your welcome to try. Otherwise , Good luck. Noel.

[NIALL HORNParticipant @niallhorn50878]

The traditional way with large diameter copper is sand filling, tight plugs at each end and lots of heat. I imagine this is still done in continental Europe where copper is used for rainwater downpipes on historic buildings. Real craftsmanship!

 

Edited By NIALL HORN on 13/02/2021 12:50:45

[Martin ConnellyParticipant @martinconnelly55370]

Noel, we bent nominal bore and OD pipes as well as OD tube, we had old tooling for BSP. All seamless and stainless. 321 sometimes but mainly 316L. Nominal bore was usually sch 5, the OD tube was defined with swg wall thicknesses and we did up to 2.75" OD and 2.5" NB. Over this we had a Hilmor MDH6 for the occasional 3" or 4" NB pipe bend we needed.

Martin C

PS the definitions for nominal bore pipes were becoming metricated. The NB pipe was coming marked up with its OD and wall thickness in millimetres as well as the inch specification. The tolerances were also noticeably improving as well which was good for bending as the requirement to cater for extremes of the tolerance band would be costly in tooling on a draw bender and where ovality had to meet acceptable limits.

 

Edited By Martin Connelly on 13/02/2021 14:17:58

[NimbleParticipant @nimble]

John,

have you considered using a specialist automotive muffler repair business to undertak your pipe bends. I believe some of them have bending machines that withdraw a central former to stop the tube collapsing.

Regards,

Nimble Neil.

[DC31kParticipant @dc31k]

Could I offer this method as an alternative?

Very simple. Just need a vice, torch, long lever, wire template…

…and 25 years of practise

[Chris Evans 6Participant @chrisevans6]

An interesting subject, I have managed to make a rear carrier for a vintage motorcycle from 12mm diameter x 1.5 mm wall section tube using a cheap DIY plumbers bending kit. I just used the formers for 15mm copper pipe and the results where good with very little if any "Necking".

For bigger diameter tubes maybe one of the motorcycle exhaust pipe makers could help ?

[HopperParticipant @hopper]

Sadly tis the nature of pipe and tube benders that you need formers of the right size to stop pipe/tube deforming while bending. Thin walled tube is even more critical than thicker walled pipe. Starndard exhaust pipe benders neck the tubing down awfully on the bend. For motorbike work where we don't want that, we usually either find a shop with a mandrel bender so the flexible internal mandrel stops necking. Or buy pre-made mandrel bends and TIG weld them together and grind the welds down. Works well with stainless for shiny finish without plating..

And around here, pipe is sold by nominal bore but tubing is sold by nominal OD. So it gets confusing. Inch and a half water pipe is a different  OD from inch and a half exhaust "pipe" which is actually tubing. Did I mention it gets confusing? Then add in metrication where inch and a half is actually called 38mm but dimensionally is inch and a half because it is made for the US market. But then some places still call it inch and a half, but they only sell it by the metre. I just take my tape measure with me…

 

Edited By Hopper on 14/02/2021 09:55:21

[Brian MorehenParticipant @brianmorehen85290]

What happen to the wood block with a hole in for bending conduit , never did get the hang of it , Copper pipe with either a internal spring or external spring was a lot better to work with . The bending machine gave us all of the answers when invented even with hydraulic models for forming bends in steam pipe. How things and times have changed .

Regards Bee,M

[Nick WheelerParticipant @nickwheeler]

Posted by Hopper on 14/02/2021 09:47:57:And around here, pipe is sold by nominal bore but tubing is sold by nominal OD. So it gets confusing. Inch and a half water pipe is a different OD from inch and a half exhaust "pipe" which is actually tubing. Did I mention it gets confusing? Then add in metrication where inch and a half is actually called 38mm but dimensionally is inch and a half because it is made for the US market. But then some places still call it inch and a half, but they only sell it by the metre. I just take my tape measure with me…

That's because the important dimension for pipe is the bore that carries material, and tube is for structural jobs so the exterior matters more

[noel shelleyParticipant @noelshelley55608]

Chris has illustrated the point very well ! 12mm od tube 1.5mm wall for it's diameter is quite thick wall. At that OD and wall it would bend nicely hot or cold. But try 25mm OD by 1.5mm wall – then the fun starts, and IF you want it to look pretty then forget exhaust pipe bends as well. There is NO easy way to bend thin wall tube and have it look nice UNLESS your going to spend BIG money ! Noel

[Swarf, Mostly!Participant @swarfmostly]

If the material didn't have to be mild steel it would sound like an application for electro-forming.

Best regards,

Swarf, Mostly!

[Nick WheelerParticipant @nickwheeler]

Posted by noel shelley on 14/02/2021 13:19:08:

Chris has illustrated the point very well ! 12mm od tube 1.5mm wall for it's diameter is quite thick wall. At that OD and wall it would bend nicely hot or cold. But try 25mm OD by 1.5mm wall – then the fun starts, and IF you want it to look pretty then forget exhaust pipe bends as well. There is NO easy way to bend thin wall tube and have it look nice UNLESS your going to spend BIG money ! Noel

Anyone who has made custom exhausts will know that mandrel bent stainless bends are easier to find and much cheaper than mild steel.

That's most of a header for a Vauxhall V6 in an MGB

[noel shelleyParticipant @noelshelley55608]

Yes Your right ! I use 4" for marine exhausts ! If I could get a cummins 903 into a B I would need 4".

BUT the OPs question was how to bend thin wall tube himself. Noel.

[David George 1Participant @davidgeorge1]

I have an industrial conduit pipe bender which has formers for 20mm and 25mm conduit. It will just bend 25mm OD thin walled stainless steel tube but I have to extend the lever, which is a 25mm solid bar about 2ft 6 inch long, with a piece of heavy duty tube about 3 feet long, to get enough leverage. I occasionally make stainless hand poles for helping unsteady people on steps and doorways or poles for bird feeders etc. Steel Conduit bends quite easily so steel conduit is quite soft in comparison to stainless tube.

David

[Martin ConnellyParticipant @martinconnelly55370]

Our specification for stainless pipe and tube for bending at work included maximum hardness values. We still had the occasional piece snap rather than stretch on the outside of the bend.

Martin C

[John MCParticipant @johnmc39344]

A belated thanks for the replies. The answer to my question as to the availability of a "universal " pipe bender was pretty much as expected, unfortunately. I think, for what I need to do, filling the pipe with something and heating is unsatisfactory.

I've asked the question elsewhere and am presently discussing with someone a method of bending that might work. The bends (in stainless steel) are little more than a "tweek" to get good alignment at the moment. At the risk of being accused of churlishness (again) I'll not say anymore just yet until we prove the idea works, or not.

If not, I think I may be buying a cheap bender off the 'bay and modifying the formers to suit.

John

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