Metal rod bending - racks

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jameso
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Metal rod bending - racks

Post by jameso » Tue May 05, 2020 9:00 pm

Anyone on here got experience of working with 4-6mm steel rod? Bending tools and methods in a workshop rather than industrial stuff?

Also contacts for batch production of a series of bends to a .DWG file could be useful.

PaulE
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Re: Metal rod bending - racks

Post by PaulE » Tue May 05, 2020 9:31 pm

I've a fair bit of experience playing with and bending rods, hot and cold, while helping kids make projects. I'm a secondary school engineering teacher, so probably no use for batch production but happy to make a 1-off or give advice.
What sort of batch size? I can ask around...
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Re: Metal rod bending - racks

Post by jameso » Tue May 05, 2020 9:47 pm

Thanks Paul. For now I'm just trying something out, bending rod with a vice. Any tips for a more accurate way? Wondered if some rounded-end pliers would do it.

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Re: Metal rod bending - racks

Post by htrider » Tue May 05, 2020 10:12 pm

Try and get a proper pipe bender. You can get cheapo plumbers ones off ebay which do copper and should manage steel. If its thin wall there is a danger of the tube creasing but you can get spring like mandrels to stop this. As with all tools you can also spend silly money....

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Re: Metal rod bending - racks

Post by PaulE » Tue May 05, 2020 10:55 pm

jameso wrote:
Tue May 05, 2020 9:47 pm
Thanks Paul. For now I'm just trying something out, bending rod with a vice. Any tips for a more accurate way? Wondered if some rounded-end pliers would do it.
If you're just after a single bend, then I'd go for holding it in a vice and using mole grips or similar to bend it. Probably teaching a grandma to suck eggs, but I always get students to draw a full-sized accurate diagram and frequently check their work on to it.

If it's a multiple bend then a selection of pliers can help, or even judicious use of a hammer to form the bend. Pins in wood are a good way of making a device to check your work against if you're making a few and want them identical. Do you have access to a torch, as some steels can have issues with surface cracks or work harden if bent cold.

A big part of it is getting used to your material and how much it springs back once you've bent it. All the above applies to rod - for tube then bending springs, sand and/or a tube bender are the way to go.
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Wotsits
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Re: Metal rod bending - racks

Post by Wotsits » Tue May 05, 2020 11:30 pm

Try to find a tube with the same radius as you're trying to bend as a former, there will be a min radius though, i think it might be roughly 7x the diameter..
Something like a short length of scaffolding pole should work great for 4-6mm tube/rod, it'll also give you repeatability..
Last edited by Wotsits on Wed May 06, 2020 12:34 am, edited 1 time in total.

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Re: Metal rod bending - racks

Post by techno » Tue May 05, 2020 11:55 pm

Wotsits wrote:
Tue May 05, 2020 11:30 pm
Try to find a tube with the same radius as you're trying to bend, there will be a min radius though, i think it might be roughly 7x the diameter..
Something like a short length of scaffolding pole should work great for 4-6mm tube/rod, it'll also give you repeatability..
The radius ratio is right for tubing it think, but for wire you can go much smaller surely? (It's a long time since I intentionally bent metal for anything).

One option for getting a batch done could be a scooter/lambretta accessories place eg; https://k2customs.co.uk/products/lambre ... -af-s-type
Even a one off could be affordable if you find a bike friendly place.

Alternatively there's engineering firms who would do it. I've No personal recommendations though.
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Re: Metal rod bending - racks

Post by jameso » Wed May 06, 2020 7:00 am

Good stuff, thanks ... Been using a small vice and a hammer or mole grips so far, reasonable and functional results. The pins in wood idea is good for checking both sides, will try that. Centring the bends so it ends up square/symmetrical is the tricky bit and a paper guide is only working to a point. I'm forming much of it as I go to see what works best. Using 4mm as it's easy to work with for testing the idea but it's too light for the intended use.

~3 to 3.5x diameter seems a minimum for bending a fork blade at the crown, or a sensible guide maybe as I've asked a builder to push it any tighter. I expect a mild steel rod will go 2.5-3x w/o too many issues. Certainly can be hammered into a tight corner bend over the vice but ends up a bit scrappy.

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Re: Metal rod bending - racks

Post by jameso » Wed May 06, 2020 7:05 am

htrider wrote:
Tue May 05, 2020 10:12 pm
Try and get a proper pipe bender. You can get cheapo plumbers ones off ebay which do copper and should manage steel. If its thin wall there is a danger of the tube creasing but you can get spring like mandrels to stop this. As with all tools you can also spend silly money....
Yes, I used a bender and springs and sand to make some convertible bar ends and aero bars (I know, aero bars :shock: ) as a GCSE Design project. Hired them and produced a pile of wrinkly alu pipes before getting it right! If I could get something like that to bend ~10mm OD pipe past 90 deg, then support sections with rod it could end up pretty light ... V3 maybe.

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Re: Metal rod bending - racks

Post by slarge » Wed May 06, 2020 8:17 am

brake pipe bending tool or small plumbers pipe bender - I got mine for about £10, and it works a treat. Bends the pipe to a (fixed) radius but without kinking or creasing. The one I have can do 6mm and 8mm pipe.

It takes all the hit and miss by using a vice and pliers out of the equation.

Not really good for batch production, but could be used if volumes are small enough

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Wotsits
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Re: Metal rod bending - racks

Post by Wotsits » Wed May 06, 2020 9:06 am

This sort of thing should do as long as the radius isn't too small-

https://www.eurocarparts.com/p/am-tech- ... gJc4vD_BwE

They usually have markings on them to get the centres right & the one above will do up to 180degree bends..
Last edited by Wotsits on Wed May 06, 2020 9:19 am, edited 1 time in total.

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Re: Metal rod bending - racks

Post by Bearbonesnorm » Wed May 06, 2020 9:17 am

I'm assuming it is bar and not tube James? You'll have an easier time with bar and it'll allow for some error when welding. Yep, a plumbers bender will cope well but it won't do intricate shapes or achieve a tight radius.

A small roll bender might be a better investment.
https://www.ebay.co.uk/itm/Heavy-Duty-M ... 0005.m1851

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Re: Metal rod bending - racks

Post by Wotsits » Wed May 06, 2020 9:23 am

Stu is da' man :ugeek:

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Re: Metal rod bending - racks

Post by jameso » Wed May 06, 2020 10:14 am

Yes, rods and no welding required. Not enough length in it to get much benefit from a larger OD tube and smaller OD will make it neater. Hadn't seen rod benders like that, thanks. Or a £9.99 pipe bender ... the pipe bend radius looks a bit large for what I'm trying to get working but once I've got a hack proof of concept I might tool up :grin: could probably make a bending fixture of the right size actually. One of those ideas that's not quite working yet but it will in theory - it'll be great if it does, and if not, well I like the process anyway.

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Re: Metal rod bending - racks

Post by jameso » Wed May 06, 2020 10:21 am

One other Q - any difference in bending stainless steel vs mild steel? Not a material I have much familiarity with. Higher elongation numbers and UTS but lower yield strength so it might form a bit easier and 5mm rod should be strong enough anyway in either. This isn't a safety-critical part but a break would be a PITA. If it's easier to form than mild steel the non-rusting would be good. Nitto seem to use chromed steel rather than stainless but I think that's due to brazing in the construction.

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Re: Metal rod bending - racks

Post by Bearbonesnorm » Wed May 06, 2020 11:40 am

any difference in bending stainless steel vs mild steel?
There is but not in this case James.
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Re: Metal rod bending - racks

Post by mfezela » Wed May 06, 2020 12:57 pm

If you know someone in the building trade. Small builders (the business not the individual)often fabricate their own rebar bender, based on this sort of principle.
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jameso
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Re: Metal rod bending - racks

Post by jameso » Wed May 06, 2020 1:03 pm

Bearbonesnorm wrote:
Wed May 06, 2020 11:40 am
any difference in bending stainless steel vs mild steel?
There is but not in this case James.
Thanks. 'Not in the case of cold-worked hacking' :grin:

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Re: Metal rod bending - racks

Post by jameso » Wed May 06, 2020 1:07 pm

mfezela wrote:
Wed May 06, 2020 12:57 pm
If you know someone in the building trade. Small builders (the business not the individual)often fabricate their own rebar bender, based on this sort of principle.
That's neat, thanks - sort of what I was thinking for a DIY tool, to drill some plate and pop some pegs (M10 bolts maybe) in the right places as a basic fixture. But no pillar drill use until I have access to my father's workshop.

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Re: Metal rod bending - racks

Post by mfezela » Wed May 06, 2020 1:30 pm

I've made a bench version of this. Three M8 bolts at suitable spacings bolted through the bench top. My worktop is only 32 mm thick. They are easily removed when not needed. A hollow tube for lever extension is needed when dealing with short lengths of rod. You will probably need some sort of secondary clamp if bends are going to be in more than one plane. Being able to access the workbench from all sides is a real boon.
Tip #1 : Do a test run with pipe cleaners or similar first to establish bend sequence.
Tip #2 Bend first, cut 'free' ends to final lengths last.

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Re: Metal rod bending - racks

Post by Bearbonesnorm » Wed May 06, 2020 2:23 pm

Ooh something I have just thought of ... welding. Remember that unless it's tigged together your welds will still rust even if you make it from stainless rod. Stainless also doesn't paint as well as mild.
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Re: Metal rod bending - racks

Post by htrider » Wed May 06, 2020 2:54 pm

This has got me thinking about pipe benders again (yes I know...) I used to have a great one on long term loan which did 6 to 13mm but I had to give it back. Looking on t'internet there doesn't seem to be anything similar. You can either get cheapo plumbers ones for small stuff or ones that only do 1/2" to 7/8".....

Unless you spend big bucks of course. I made numerous motorcycle racks and mudguard stays using it and have often thought of making bicycle racks or varying types......

Of course then I'd need a tig welder

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Re: Metal rod bending - racks

Post by jameso » Wed May 06, 2020 5:13 pm

No welding needed for this one Stuart, I'm trying to get a braced/tensioning thing working. Purely bent rod and cunning (ie, setting myself up to fail :grin: )

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Re: Metal rod bending - racks

Post by jameso » Wed May 06, 2020 5:17 pm

mfezela wrote:
Wed May 06, 2020 1:30 pm
I've made a bench version of this. Three M8 bolts at suitable spacings bolted through the bench top. My worktop is only 32 mm thick. They are easily removed when not needed. A hollow tube for lever extension is needed when dealing with short lengths of rod. You will probably need some sort of secondary clamp if bends are going to be in more than one plane. Being able to access the workbench from all sides is a real boon.
Tip #1 : Do a test run with pipe cleaners or similar first to establish bend sequence.
Tip #2 Bend first, cut 'free' ends to final lengths last.
That's it, d'oh.. I've just drilled a piece of wood as a bending tool and realised I need to put it in the vice that also needs to hold the work at stages - V2 will be direct into the bench : ) workflow thinking.
Sequence was planned with coat hangers. I ordered her indoors a load more off ebay after doing similar for the front bag system last summer... used 4 coat hangers to get the centre-out bends and distances worked out. This one will take more I think.

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Re: Metal rod bending - racks

Post by belugabob » Tue Jun 16, 2020 8:25 am

jameso wrote:
Wed May 06, 2020 5:13 pm
No welding needed for this one Stuart, I'm trying to get a braced/tensioning thing working. Purely bent rod and cunning (ie, setting myself up to fail :grin: )
Over the handlebars and under the stem?
Had a mess around with something similar, but haven't really got the workshop facilities to do it accurately enough

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