Routing aluminium

[redx]

Hi,
I'm trying to bend 1" stainless tubing and have made a diy bender out out wood similar to this one found on youtube.

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Trouble is, it doesn't work. The wooden formers, which have grooves routed in them, are too soft to withstand the strain, particularly at the centre bolthole where the most strain occurs. I thought of using aluminium instead of wood but the expense would be too great for my project. It got me wondering though, is it possible to rout a groove into aluminium using a woodwork router?

And can anyone suggest a way of strengthening the pictured setup to make it work? I fitted some bronze bushes to the centre holes but they made little difference. the plywood is just too soft I think.

redx

[BobL]

Hi,
I'm trying to bend 1" stainless tubing and have made a diy bender out out wood similar to this one found on youtube.

Trouble is, it doesn't work. The wooden formers, which have grooves routed in them, are too soft to withstand the strain, particularly at the centre bolthole where the most strain occurs. I thought of using aluminium instead of wood but the expense would be too great for my project. It got me wondering though, is it possible to rout a groove into aluminium using a woodwork router?


Short answer is yes - this has been discussed many times on the forum e.g. http://www.woodworkforums.com/showthread.php?t=182972&highlight=Router+Aluminium

As for the SS what are the wall thickness of the tube?
It is probably work hardened from the tube making process and you will have to use steel formers.
You might have better success if the SS is annealed first - this involves heating to red heat and then dunking it in water (yes it is the reverse of Carbon steel)

[redx]

Hi BobL,

Thanks for the reply. I posted this thread in the woodwork forum as well and got a few replies over there.

What I'm trying to do is build a new s/steel bowrail for my boat. I got the idea of making the formers out of plywood from a Youtube video. The guy who posted the video said the system worked well for him but he was only bending 7/8" s/s tubing. My stainless tube is 1" OD, not sure of wall thickness but it's more than 1mm so it's probably 1.6mm. I modified the design of the youtube bender after I found it wasn't going to work for me. The picture below shows what I came up with using the scrap steel I had laying around. It did bend the tubing ok as you can see in the photo and the groove for the tubing seems to be able to cope but the strain is too great for the plywood at the centre bolthole. The hole becomes larger and elongated as the wood compresses. I've fitted bronze bushes to try to overcome that problem but it was to no avail.

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My next plan is to sandwich the wooden formers between two circular 1/8" steel plates, The bolt will then pass through the steel plates as well as the wooden former and hopefully this will stop the distortion of the centrebolt hole. I'll also have to go up a couple of sizes with the centrebolt diameter. I was using 1/2" centrebolts but they're not strong enough.



Cheers,
redx.

[jhovel]

See your other thread. Incidentally, with a well compacted sand filed tube, you don't necessarily need profiled formers.

[Michael G]

Incidentally, with a well compacted sand filed tube, you don't necessarily need profiled formers.

Be careful about the type of sand though. I once used something labelled as "Paving sand". Turns out that it had resin binders in it so that the sand formed a solid mass in the tube once heated and bent. :doh:
Took some time to get it out.

Michael

[redx]

Thanks fellas,

Using sand (the right sand) is good advice, I'll give it a go.


Thanks,

redx.

[Oldneweng]

I have 43 acres of sand and believe me it does not stick together.

Dean

[redx]

Well, I gave my diy bender a go using 1" stainless steel tube packed with sand. The sand did improve the finished bend although there was still some flattening, but I think it is within acceptable limits and doesn't look bad (see pics). Good enough for me anyway.

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Thanks for the advice.
redx.

[jhovel]

Great outcome! Well done. Give us a bit more detail on how you went about it - for the education of people who want to embark on a similar venture.

[redx]

Great outcome! Well done. Give us a bit more detail on how you went about it - for the education of people who want to embark on a similar venture.

Hi Joe,

Thanks for the comments.

As said in my first post I started off bybuilding the same setup with plywood formers as shown in the youtube video atthis link.

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

In the video the small wooden former wasfixed in place with a bolt through the benchtop, but it was free to rotate. The large wooden former, aslo bolted throughthe bench did all the bending by rotating the tubing which was held in placeagainst it by a piece of aluminium strapping. The guy in the video said itworked fine for his 7/8" S/steel tubing but in fact you don't actually getto see the thing in action. Unfortunately that setup wouldn't look at my1" tubing and didn't work for me at all. So I set about modifying it untilI came up with a bender that does work. he following pics show the result.

Steel or aluminium formers would workbetter of course but I didn't have the means to make them so I used wood. Atfirst I made both the large and the small diameter formers out of plywood, asin the video, but plywood proved to be to soft for the smaller wheel so I remadeit using an Australian hardwood.

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As with the youtube video I first made theformer wheels by cutting circles of plywood then used a 1" cove bit to router a groove around the edge of thecircles. I then bolted the two halves together using about a dozen 5/16"bolts. However, in my modified version these bolts holding the two halvestogether would be in the way so I removed them and used epoxy resin to glue thehalves together instead. I also filled all the now unused bolt holes with resinfor extra strength

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In my bender the smaller wheel does all thework, with the larger wheel bolted in place to stop it from rotating. At firstI had both wheels able to rotate but this allows the tubing to slip out ofposition and I found it better to have the larger wheel stationary. I also madea small block of hardwood with a 1" groove to clamp the tubing in place sothat it cannot move during the bending. The 3/8" mildsteel flat bar usedin the building of this bender is probably a bit of overkill but it was what I hadon hand at the time.

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Originally I used 1/2" nickel platedbolts for the centrebolts of the former wheels but they soon bent under thestrain so I changed to 1/2" High tensile bolts and these hold up well. Asthe large former wheel rotated while bending the tube the centre-hole in theplywood became distorted, so I drilled the hole larger and fitted bronze bushesto strengthen it. This was probably not necessary because around the same timeI realised the large wheel needed to be fixed in position and not allowed torotate at all.

If I was to make another of these woodenbenders I would use hardwood for both former wheels and pay more carefulattention to the routering of the grooves. These have to be close fitting tothe diameter of the tubing. The groove in the large wheel you see in the picsis a smidgen larger than my tubing and I believe this is what is causing theslight flattening of the tube during the bending process.

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This bender doesn't do a perfect job as itis, but it is good enough for the few bends I need. Perhaps with a bit moretweaking it could be improved. You will see in the pics that I am using aworkbench in the open in my backyard. This is because I only have a smallgarage/workshop and it's now almost completely filled with my (almost finished)boat. There was no room for the bench so it was relegated to the yard for thetime being.

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Hope you can all make sense of this blurband that is of some help to someone.

Cheers,
redx

[jhovel]

Thank you!
Very nice description, photos and analysis of the shortcomings, along with suggestions or improvements. That's exactly what's needed to help us learn too.
Great stuff!

[redx]

I've posted a pic of my new bowrail (almost finished). My home-made bender was used to do all the bends and it turned out fairly well I think.

redx.