andrew morrall
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| posted on 29/9/05 at 05:57 AM |
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To heat or not to heat
Should one heat ali sheet when bending it?
Should you only heat the sheet for compound curves?
How hot should it be?
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donut
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| posted on 29/9/05 at 06:22 AM |
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Ally is so soft that i have never heated it and i don't know anyone who has.
Andy
When I die, I want to go peacefully like my Grandfather did, in his sleep -- not screaming, like the passengers in his car.
http://www.flickr.com/photos/andywest1/
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Mix
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| posted on 29/9/05 at 06:29 AM |
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Andy, I think most people who have used alloy for the rear panel will have annealed it around the compound curves. 
Andrew, the normal way to anneal alloy is to spread soap on the area concerned and then heat, (from the other side) with a blowtorch until the soap
turns brown. Allow to cool and continue to form the alloy, repeat the process as required.
Mick
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DaveFJ
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| posted on 29/9/05 at 12:25 PM |
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tried heating some duralumin sheeting (2.6mm) then hit it with the hammer and it shattered!! 
Dave
"In Support of Help the Heroes" - Always
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Hellfire
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| posted on 29/9/05 at 03:26 PM |
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quote:
Originally posted by DaveFJ
tried heating some duralumin sheeting (2.6mm) then hit it with the hammer and it shattered!!
Blimey - first time I've heard of that! 
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britishtrident
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| posted on 29/9/05 at 04:05 PM |
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Duralumin (wot Zepplins were made of) is from aluminium copper alloys it quench hardens from 500-550c indeed it continues to harden over several
days --- its not the heating that hardens and it but the high rate cooling from a very high temperature.
More "normal" aluminium alloys both age and work harden but nothing like to the extent of "Dural" Like Mix says gentle
heating followed by cooling puts it back into maleable/ductile state and gets rid of the stresses caused by working it.
an eletric hot air gun should provide just enough heat.
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DaveFJ
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| posted on 29/9/05 at 06:59 PM |
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yes in hindsight a blow torch was a bit excessive....
Dave
"In Support of Help the Heroes" - Always
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planetester
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| posted on 29/9/05 at 09:17 PM |
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pure ali is very soft & does not harden, whats called T4 is harder but will anneal with heat as described above & does not work harden if you
raise the temp enough, T6 is even harder but again can be annealed at the right temp, to harden it again you need to accurately controll the temp
& the quenching
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