Bending aluminium bar

[GraemeVW]

I need to bend some aluminium for a project I'm making. Not my normal range of experience so I've not thought it though.
I bought some 16mm square bar and I need to roll it into a circle with an internal diameter of 275mm.

No problem thinks I. Buy aluminium, bend it.

Aluminium turns up, reality hits. I'm not just going to bend that by hand am I!
Bent it a bit with some big mallet blows, but that's obviously not the way either.
I have no rolls.

So, hope workshop style, what are my options? Even worth trying to find ways to do it cold?
A friend has oxy/acetylene so i could use that. Would need a former though. But then trying to bend it cold looks like it would too.

For a one off job would I get away with a wood former? A disc the right size, screwed to another board. Some kind of stop to trap the loose end. Heat the outer edge a few inches at a time until it forms?
Or am I just going to set light to the wood?
Not sure how hot I'll need to get it.

Should have thought this through...

 

[GraemeVW]

If it matters, I have 1m of stock, and I don't really need a FULL circle, 3/4 in a C shape is what I need to achieve.

 

[GraemeVW]

Only other thought is to use 3 vertical bits of round bar in the vice and try and 'press' it every inch.
Wanted to avoid distorting it in a way that makes the inner face taller than the outer face though.


Edit, tried, vice isn't going to work. Even my record 112 isn't really going to do that.

 

[Shox Dr]

you need a ring roller

 

[GraemeVW]

you need a ring roller

Yep. I know that now
Was immediately obvious as soon as I took the stock out the packaging.
No idea wjyni thought I'd "just bend it".
I'm not used to aluminium, it's not as bendy as if expected

I need to find the best way with what's available to me now though.

Although I want it to be as accurate as I can get it, it's worth pointing out that in use, it will never be seen, so doesn't need to be a perfect square section hoop.

 

[Agroshield]

Could you make it from two pieces of 16 x 8 epoxied together? Or three pieces of 5, 6 and 5mm thick? Those would bend cold over a wooden former and a ratchet strap to keep everything in place while the glue sets.

 

[Guzrik]

Fwiw someone with a rotarytable and a mill could machine one from a plate, accurate and easy?

 

[GraemeVW]

Could you make it from two pieces of 16 x 8 epoxied together? Or three pieces of 5, 6 and 5mm thick? Those would bend cold over a wooden former and a ratchet strap to keep everything in place while the glue sets.

Possibly, yes.
The ring will be a starting point for what I need to make.
Making the ring in layers will make some of the next steps harder, but probably also some of the next steps easier.

 

[Hopefuldave]

I wouldn't bend it hot, a lot of aluminium alloys are "hot short" and get increasingly brittle with temperature - what I was taught (by the cycle mechanic for the 1952 Olympics) was rub soap on the ally, heat until the soap turns brown/black, then quench in cold water to anneal it (exact opposite of ferrous metals!). Hardness will return over the next few days. Certainly worked on my ally Cinelli handlebars!

Dave H. (the other one)

 

[GraemeVW]

Fwiw someone with a rotarytable and a mill could machine one from a plate, accurate and easy?

This was my first thought. There will be another piece attached to the ring, it could all be machined at once.
But expense of getting a 16mm thick , 275mm internal and 330mm external ring machined would be more than the project could bear.
Hence me buying bar to bend. Just hadn't trigger how awkwardly would be to do with limited tools.

 

[GraemeVW]

I wouldn't bend it hot, a lot of aluminium alloys are "hot short" and get increasingly brittle with temperature - what I was taught (by the cycle mechanic for the 1952 Olympics) was rub soap on the ally, heat until the soap turns brown/black, then quench in cold water to anneal it (exact opposite of ferrous metals!). Hardness will return over the next few days. Certainly worked on my ally Cinelli handlebars!

Dave H. (the other one)

Ok. I could try annealing it. I'll look up what sort of temperature is needed. I've heard the black soap thing before, I just don't know what kind of temp that is and therefore the easiest way for me to get it there.

 

[Hopefuldave]

Ok. I could try annealing it. I'll look up what sort of temperature is needed. I've heard the black soap thing before, I just don't know what kind of temp that is and therefore the easiest way for me to get it there.

Doesn't take much, something like a plumbers' Bullfinch torch is plenty - I've long ago (as in a couple of generations...) done it with a paraffin pump-up blowlamp. Important thing is to heat it evenly, so all's at the same sort of temp before quenching.

Dave H. (the other one)

 

[Mick Annick]

I wouldn't bend it hot, a lot of aluminium alloys are "hot short" and get increasingly brittle with temperature - what I was taught (by the cycle mechanic for the 1952 Olympics) was rub soap on the ally, heat until the soap turns brown/black, then quench in cold water to anneal it (exact opposite of ferrous metals!). Hardness will return over the next few days. Certainly worked on my ally Cinelli handlebars!

Dave H. (the other one)

‘52 would have been around the time my wife‘s grandfather was coaching an olympic cyclist!

 

[GraemeVW]

Doesn't take much, something like a plumbers' Bullfinch torch is plenty - I've long ago (as in a couple of generations...) done it with a paraffin pump-up blowlamp. Important thing is to heat it evenly, so all's at the same sort of temp before quenching.

Dave H. (the other one)

The difficulty will be evenly heating a 1m length

 

[Hopefuldave]

‘52 would have been around the time my wife‘s grandfather was coaching an olympic cyclist!

Small world! Ever mention Wally the mechanic? He ran the Proper Racer shop in Weybridge, bought a lot of my Expensive Parts for my time trial bike there

Dave H. (the other one)

 

[Hopefuldave]

Ill probably slso see if i can find a shop nearby

The difficulty will be evenly heating a 1m length

Move the torch...

Dave H. (the other one)

 

[GraemeVW]

Move the torch...

Dave H. (the other one)

I guess I'm over thinking the whole evenly thing.

Just saw a YouTube vid, they used sharpie. The ink disappears at the right temp. Then they let it air cool and it was super bendy.

 

[Agroshield]

There will be another piece attached to the ring, it could all be machined at once.

What does the entire thing look like in plan view? Could you have it laser profile cut and laminate it up to 16mm in the opposite plane to my suggestion above? If it is only 3/4 of a circle, the parts might nest quite well.

See post #14 here for concept: https://bbs.homeshopmachinist.net/forum/general/53115-build-your-own-steady-rest

 

[GraemeVW]

What does the entire thing look like in plan view? Could you have it laser profile cut and laminate it up to 16mm in the opposite plane to my suggestion above? If it is only 3/4 of a circle, the parts might nest quite well.

See post #14 here for concept: https://bbs.homeshopmachinist.net/forum/general/53115-build-your-own-steady-rest

I will draw it out later, but yes, that would probably work.
It's basically a spacer.

The main issue is cost. Bit of bar and bend it up was about the budget for this.

 

[zzr1200]

So do you need 1 or 2 rings made, (275mm internal and 330mm external ring)???