Will I succeed bending AL sheet?

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ctwo
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Will I succeed bending AL sheet?

Postby ctwo » Fri Nov 17, 2017 3:49 pm

I have a few pieces, probably 1/16", that I want to make 90° bends to build a box. If I use a propane torch, would I likely be able to avoid cracking - using my brake?
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GlennW
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Re: Will I succeed bending AL sheet?

Postby GlennW » Fri Nov 17, 2017 4:02 pm

Depends on the alloy and temper.

5052-0 would need no heating.

Either way, increasing the bend radius is preferred to heating.
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Re: Will I succeed bending AL sheet?

Postby Harold_V » Fri Nov 17, 2017 4:56 pm

One thing to consider--is that aluminum sheet has grain. If it's heat treated, it will readily bend across the grain, and, as Glenn said, the greater the radius, the better chance you'll have of success. However, it will likely fracture if you bend parallel to the grain. It is for that reason that you would be best served with 5052-0.

Heating aluminum to bend is not recommended, although you can use heat to anneal the piece before attempting the bends. That will most likely eliminate any risk of breaking, but leave the aluminum dead soft. If that be your choice, heat, then water quench the aluminum. You can use soot from an acetylene torch to know when to stop heating. The moment it starts to burn off, it's time to quench. Any further heating will result in melted aluminum.

H
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ctwo
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Re: Will I succeed bending AL sheet?

Postby ctwo » Fri Nov 17, 2017 9:26 pm

I'm looking at the material and I can see what I think is grain, and the mfg has bent it both ways, about 1/8 radius. It looks great! My HF brake has a sharper plate to bend against, cut about 30 degrees.
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GlennW
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Re: Will I succeed bending AL sheet?

Postby GlennW » Fri Nov 17, 2017 10:04 pm

Bend a two inch wide strip of aluminum over the sharp edge of your brake and then with it in place bend the piece you need.

That will cover the sharp edge and increase the radius.

More than one strip can be used to get the bend radius you want.

Also, file and polish the edges of the sheet you are bending to eliminate stress risers and it will be less likely to crack when bent.
Glenn



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Harold_V
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Re: Will I succeed bending AL sheet?

Postby Harold_V » Sat Nov 18, 2017 2:14 am

ctwo wrote:the mfg has bent it both ways, about 1/8 radius.

Given that bit of information, it's likely going to work just fine, but I'd suggest you follow Glenn's advice, as it can't hurt.

If the items in question were intended to be used in a stressed condition, it's possible that they were artificially aged after they were formed. If that's the case, they'll likely break instead of bend when you work parallel to the grain. However, if the material is not heat treated, or if it's a non-heat treatable grade, you're likely good to go.

Make sure you report on the results, so others might benefit.

H
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Rich_Carlstedt
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Re: Will I succeed bending AL sheet?

Postby Rich_Carlstedt » Sat Nov 18, 2017 5:50 pm

A easier way instead of soot, is to use a black magic marker and draw it along where your bend lines will be.
Then heat it with a torch until the ink fades , which is the same as the soot burning off, about 400 degrees F
Just slowly use the torch along the line. no need to heat the whole sheet. Bend as quickly as possible after the heating is done.
Aluminum self hardens over a period of time, about 30 days

The suggestion to use a two inch wide piece is a good one
Another trick to use with your brake is to run a strip of Scotch Tape on the brake edges and bender. The tape will allow the bend too form over a softer edge which prevents scratches on the aluminum and a better chance of success for a smoother bend
Rich

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Re: Will I succeed bending AL sheet?

Postby Atkinson_Railroad » Sat Nov 18, 2017 7:19 pm

What is the Alloy and Temper of the aluminum?

Until that question is answered, all opinions written here, are just........ Ya.

Hard aluminum tempers are difficult to form in a hobbyist's shop environment. Soft aluminum tempers are easy.

If you're having an issue forming the aluminum sheet you have on hand, it's likely a hard temper not suitable for forming in a home shop equipment.
I vaguely remember "Aluminum Forming" published by Reynolds Metals Company was added to the resource library here at chaski quite a while ago.
If not... my memory is corrupted.

Trying to bend/form aluminum not intended to be cold formed in a hobbyist environment can lead to being frustrated.

John

jcfx
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Re: Will I succeed bending AL sheet?

Postby jcfx » Sat Nov 18, 2017 7:31 pm

Rich_Carlstedt wrote:A easier way instead of soot, is to use a black magic marker and draw it along where your bend lines will be.
Then heat it with a torch until the ink fades , which is the same as the soot burning off, about 400 degrees F
Just slowly use the torch along the line. no need to heat the whole sheet. Bend as quickly as possible after the heating is done.
Aluminum self hardens over a period of time, about 30 days


Sharpie brand markers work well for that trick, they started marketing an industrial version that
will take up to 500º F before disappearing, red labeling on the pen barrel as opposed to the
black labeling. Personally I don't see much difference between them as a temp indicator for aluminum.

There is also another trick using just a bar of Ivory soap, use the bar of soap to make marks on the aluminum and heat till the marks turn black.

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ctwo
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Re: Will I succeed bending AL sheet?

Postby ctwo » Mon Nov 20, 2017 11:50 am

Thanks all for the tips and insights.

The best I can tell about the material and temper is that it is weathered scrap. I kind of went a different route with my original plan, but still ended up bending some C-channel that I had notched in some V's. I just set the channel on the NG stove until it hit its max temp, then quenched. This stuff is really soft anyway and bend a large radius free-hand. The one sheet I tried to use the brake would not bend on my brake, because I was trying to bend a very short tab and it would just flex my brake and push back, so I used the bench vice and tapped it over. It was fine.

Sheet metal work, I really do not like it, and the product of my work shows it. It was for me and is functional.
Standards are so important that everyone must have their own...
To measure is to know - Lord Kelvin
Disclaimer: I'm just a guy with a few machines...


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