Bending ally

[WolfieParticipant @wolfie]

[WolfieParticipant @wolfie]

I have a length of 10mm aluminium which I want to bend in 2 places.

Do I simply bend it or will it crack or anything. Do I need to heat it?

[michael burton 1Participant @michaelburton1]

there is a possibilty that it will stress crack iv had that problem before goes like a crazed surface finish i supose it depends on how servere the bends are……… you can anneal ally one way i was taught was to use a sope i think you can use normal soap or washing up liquid as a temputure quide when it goes i belive it was a browny colour it is at the right temputare, and should bend with out any stress cracks forming

 

Edited By michael burton 1 on 03/03/2012 18:34:20

[MadMikeParticipant @madmike]

Wolfie, what width is the bar? What form is the bend to take, what angle, what inner radius etc? What is distance between the bends? What is the finished item to be used for?

Remember that you will be stretching the outer skin of the bend and compressing the inner. If the internal rad is too small, and the angle is acute then you may simply cause the aluminium to fail.

A bit more info will help in giving advice on how to do the bending. HTH.

[WolfieParticipant @wolfie]

Width?? Its 10mm round bar.

I simply want to bend a length 90° and then 90° again to make an open ended rectangle around 18" long and 5"wide.

It will not be load bearing.

[nigel jones 5Participant @nigeljones5]

should be fine in my experience but depends massively on the quality of material. The crap they sell at b&q is made from melted down fridges and just cracks – their copper is even worse!

[nigel jones 5Participant @nigeljones5]

dont be tempted to heat it – i tried this and it was a complete disaster!!

[Gray62Participant @gray62]

Posted by nigel jones 2 on 03/03/2012 21:29:29:

dont be tempted to heat it – i tried this and it was a complete disaster!!

Hmm, maybe the method employed may have been at fault here, without more info it is hard to judge.

Heating ally or its composites always presents problems. In most cases the methods decribed above will prove effective. Everyday washing up liquid is an adequate indicator of the correct temperature. Once the soap turns dark brown, the ally will have reached the required temperature to be 'annealed' The indicatore (soap) should be on the opposite site to that which heat is applied. Keep the torch moving all the time.

It can then be worked into shape. If there are numerous shaping operations, then the ally should be annealed after each process is complete in order to relieve stresses and allow the materiel to take up complex shapes.

CB

[Martin WParticipant @martinw]

Wolfie

You haven't said what radius you are intending to bend the bar to. As MadMike says too tight a radius and the bar is likely to deform and fail.

I've used the soap method, as described by CoalBurner, to anneal aluminium sheet prior to bending and it works fine. I also think its OK for hard aluminium alloys like duralumin though it may need to be repeated during the bending process if particularly sharp bends are being formed as some of these alloys tend to work/stress harden.

Cheers

Martin

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

Hi Wolfie ,

All materials and all cross sections of bar have two critical bend radii . Any bends tighter than the lower critical radius are likely to crack and all bends easier than upper critical radius are unlikely to crack .

For cold worked low alloy aluminium round rod these two critical radii are approx 2.5 D and 3.5 D based on the rod centreline radius and rod diameter D .

So for your 10 MM round bar cracking is likely at inside radius of less than 20 MM and unlikely at inside radius greater than 30 MM .

These critical radii can be determined theoretically these days but where mostly arrived at by accumulated practical experience of many people .

Tighter bends can be produced safely with annealing and or preconditionng of the bar and by specialist bending processes but these are all tricky to get right for a one off bending job .

MW

 

Edited By MICHAEL WILLIAMS on 04/03/2012 00:17:49

[Mark P.Participant @markp]

Wolfie,remember that aluminium has a grain running along it similar to wood,always try to bend across the grain,also polish the sides of the bend to reduce the possibility of cracking.Annealing it should help with bending go with the soap method.

Pailo.

[Sub MandrelParticipant @submandrel]

Wolfie

If it is aluminium alloy, not pure aluminium, it will probably age-harden within hours or days, so anneal it with the soap method and bend straight away. There are ways to maximise the re-hardening but it will probably get as strong as you need in a day or two anyway.

Neil

[WolfieParticipant @wolfie]

Whats annealing?

[jason udallParticipant @jasonudall57142]

annealing s heat treating metal[mostly] so that when cooled the metal remains ductile

work hardnen able material like aluminimim alloys , copper, bronze [infact most stuff except steel] and some steels [ yeh I know] work harden and as part of that crystals form and grow

these crytals initally slide past each other when bending and forming the metal

once grown large enough they no longer slide but jam and the metal is "work hardened" futher bending /forming just breaks the material.

annealing resets the crystals to the initial small size ready to repeat the working

hardening …as with steels is again effecting the crystal boundries [small for ductile large for hard] but to have to opposite effect ..you heat steel above what is known as the transition temperture and rapidly cool to control the crystals[in steel usally called grains].

tempering is fine tuning the balance of properties.

in short anneaing application of heat and cooling to softern or remove work hardening from a materal

[Author]

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