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Old 05-09-2017, 10:13 AM
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heinke heinke is offline
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Question Door skin fabrication tips and tricks??

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Originally Posted by heinke View Post
Shaping and attaching door skins is coming soon. I've never done that before and am hoping to not contribute more pieces to scrap bin

I bought a couple of sheets of Al 5052, .063 as I've heard that's a better alloy for door skins. Fortunately, the door skins on this body are mostly curved in only one direction, thus almost no compound curve to worry about.

Do you guys have any tips and tricks for making/attaching door skins that can help me out?
I put this request up in the GTO build thread, didn't get any answers, so putting it up here for more visibility.

I did see this video on making a door skin, https://www.youtube.com/watch?v=5oFsHldmjDU Most of it made a lot of sense to me but the annealing part left me baffled. I'd think you'd want the door skin to retain as much of the work hardening as possible for dent resistance. Is the annealing required for the edge folding/hemming to minimize cracks? I don't recall that he gave the alloy grade used in the video. I've hemmed 3003 without any crack issues, is this something needed for 5052 hemming?
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Old 05-09-2017, 11:45 AM
steve3 steve3 is offline
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the section being annealed is the top of the skin, complicated area... start video at 6.00 and you can see the finished flange for the window edge, annealing allows him to shape that section without pulling the shape out of the reverse curve below, this guys done a few of them id say lol. Normally you shouldnt need to anneal a simple closed flange, more critical is the size of the flange being made smaller in a rounded corner
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Old 05-09-2017, 02:54 PM
bobadame bobadame is offline
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You'll want to be careful bending a tight 180 degree bend parallel to the grain. This is where it's prone to crack. Don't know that it will but if it does, that's the most likely place for it to happen. Probably worth doing a test bend or 2 on a small piece.
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Old 05-09-2017, 03:59 PM
crystallographic crystallographic is offline
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When hemming door/hood/lid skins of 3003, 5052 and 6061 it is "advisable" to anneal exactly the bend zone /area - hot sharp flame moving at the "right" speed and the wet quench following on.

Not the flange. Not the skin.
Just the bend area/line.
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Old 05-09-2017, 04:43 PM
Marc Bourget Marc Bourget is offline
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For the sake of accuracy, (following is from my recall of the discussion in "Forming Alcoa Aluminum) "annealing" with a torch isn't, technically, "annealing". It's "taking the material to 'W' temper" or, in other words, relieving it from work hardening.

As I understand it, if the material work hardens, like 6061, it will go back to the T4 state after "W" temper as a result of further working the metal and aging.

No, I'm not saying you have to stop using the term "anneal" just think it's better for the uninitiated to know there's a difference.
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Old 05-09-2017, 07:20 PM
Mike Motage Mike Motage is offline
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Thanks Kent, I'd wondered if annealing just the edge would work. Your explanation is understandable for me.
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Old 05-10-2017, 12:56 AM
Maxakarudy Maxakarudy is offline
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I thought it strange to anneal after shaping the door skin, when I've annealed a new flat panel it warps quite a lot and you do need a door skin to work hard to keep it's shape, but then I use 1050/3003 60 tho.
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Old 05-10-2017, 12:33 PM
crystallographic crystallographic is offline
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Quote:
Originally Posted by Maxakarudy View Post
I thought it strange to anneal after shaping the door skin, when I've annealed a new flat panel it warps quite a lot and you do need a door skin to work hard to keep it's shape, but then I use 1050/3003 60 tho.
I turn the hood/door/lid skin edges both ways - strike and turn - or strike, soften and turn. It depends on the shape of the skin at the edge needing turning, such as a reverse - where the flange needs some serious stretching to go around .... and by the time you have the shape in the flange you are only halfway home....???

Or on corners, where the flange has to reduce a bunch to make the curve ... shrinking when soft is a bit easier than when hard ...?

Or when the crown is high on the skin and the edge has to shrink over a distance - and keeping the shape of the skin whilst turning the edge is important enough that I soften the edge while turning it and also reducing its length (shrinking).
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Old 05-10-2017, 12:37 PM
crystallographic crystallographic is offline
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Quote:
Originally Posted by Maxakarudy View Post
I thought it strange to anneal after shaping the door skin, when I've annealed a new flat panel it warps quite a lot and you do need a door skin to work hard to keep it's shape, but then I use 1050/3003 60 tho.
I turn the hood/door/lid skin edges both ways - strike and turn - or strike, soften and turn. It depends on the shape of the skin at the edge needing turning, such as a reverse - where the flange needs some serious stretching to go around .... and by the time you have the shape in the flange you are only halfway home and the flange is starting to crack from work-hardening ....???

Or on rounded corners, where the flange has to reduce a bunch to make the curve ... shrinking when soft is a bit easier than when hard ...?

Or when the crown is high on the skin and the edge has to shrink over a distance - and keeping the shape of the skin whilst turning the edge is important enough that I soften the edge while turning it and also reducing its length (shrinking).

But yes, when the skin is "flat" and the edge is straight, then the strike and turn method is reasonable.
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Old 06-09-2017, 10:37 PM
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heinke heinke is offline
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Question More door skin questions

Thanks for the information provided so far.

Ok, I'm in the middle of my first door skin and now have more specific questions. I've cut and shaped the skin so it fits well to the inner door frame so I'm beyond that stage. I was just about to anneal the bend zone as advised and then decided to do a test piece to get some experience before doing the actual piece.

I'm most concerned about the curved edges where the skin will need to shrink as it's hemmed over so I made sure my test piece had one of those. After wrestling around and butchering the first test piece, it became clear I wasn't anywhere near ready for the real thing.

I did a 2nd test piece, it came out better but still pretty much a hack. So I now have a bunch of questions.

Annealing
  1. Al 5052 .063 thickness. Although not marked on the sheet with the alloy, I bought at very reputable supplier and they confirmed it was 5052 when I picked it up. This stuff is tough, I’d estimate about half again as hard to cut as 3003 with aviation snips. But probably twice as hard to bend as 3003. Does this sound like what’s expected for Al 5052?
  2. The metal doesn’t seem to soften much with annealing. I tried using 650 degree tempstick but it wouldn’t mark/stay on surface of aluminum, so I had to use the soot method. I started with “light” soot, metal didn’t soften so I went to “heavy” soot. This seemed to work better but metal never softened near what I experience with annealed 3003. The metal surface got a rainbow color after annealing. Is this expected?

  3. Anneal both sides? Seemed to soften the most (but still not that soft) when I anneal on both sides. Is this really required? Or am I doing something wrong here?

Hemming
  1. On a straight edge, how much metal should result on backside of hem? My first thought was about 3/8”, but on test piece this amount felt almost excessive. Is ¼” enough?
  2. On a curved edge, how much on hem backside? On test piece, 3/8” resulted in a lot of deformation during hemming operation and still warped when done. On test piece, ¼” had less deformation but still more than I’d like. Is 1/8” on backside of completed hem enough?
  3. Should I mechanically shrink the curved edge hem area prior to or when it’s turned to a 90 prior to final clamp? On the test piece without mechanically shrinking, it seemed to deform the skin more than shrink the metal that ended up on backside of hem.
  4. Multiple annealing during hem? Whatever softening achieved during initial annealing, seem to go away quick once the metal was bent. Should the bend area be annealed a second time? Several times?

I’m asking all these questions because the inner frame is Al 3003. I’m concerned that it will get pulled and deformed during the hemming of Al 5052 skin.
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