Summarizing Annealing of Aluminum...Do I have it right?

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Summarizing Annealing of Aluminum...Do I have it right?

Postby cracker39 » Tue Jun 13, 2006 9:14 am

I’ve been reading several past posts on annealing aluminum trim. Is there a primer for doing this on the site? If not, all of the information on annealing should be put into one set of instructions under the Important Information topic.

I’m going to look for some aluminum angle today or tomorrow (depending on Alberto’s mood), probably 3/4” or 1” x 1/2” as I need to screw the wide side down onto the roof and extending down the front and back corners, so that the narrow side of the angle covers the edges of the roof and front/back 1/4” plywood. (That also means a visit to HF for a metal punch.)

Here’s what I think I have learned about annealing. Please correct me if I am wrong and/or add any comments if I left anything out:

1. Use a candle to apply a light, even coating of soot to the aluminum (I presume that means to the inside of the angle by some of the photos I saw).

2. Use a propane torch to heat no more than a 6” section at a time until most, but not all, of the soot burns off, keeping the flame moving. Don’t overheat as aluminum trim will melt if too much heat is applied…when the flame appears to start turning orange, move on to the next section immediately. (Use a scrap piece to test to see how much heat will melt the aluminum, then stop short of that point when annealing for real.)

3. Allow the aluminum to cool slowly.

4. Install the aluminum trim by positioning one end, inserting a couple of screws, bending it down to follow the curve, and applying screws as you go to hold it flat. Flatten kinks or ripples in the other edge with a rubber or plastic head mallet. Using blocks of wood against the aluminum will prevent denting and allow use of a regular hammer. If the bend is too tight, you may need to cut some kerfs into the outer edge.

5. After annealing, bending the aluminum will cause it to re-harden. It can be annealed again if additional bending is required.

Additional questions:

1. Screw holes. How much distance between them. I'd assume 4" on curves, maybe up to 6" on flat sections?

2. Screw holes in aluminum should be punched, not drilled? Before or after annealing? Or does it matter when?

3. What type of screw should be used with aluminum trim (steel, aluminum, etc.) Or does it matter?

4. Aluminum can be painted after proper priming, right? What type of primer is needed? Will the common "sandable primer" in spray cans work? I want mine painted white.

Did I learn my lessons? Thank you.
Dale

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Postby Bandit » Tue Jun 13, 2006 9:43 am

I used a MAPP Torch (w/Oxygen) that puts out a blue (hot flame). The soot is acting as a temperature sensor. When the soot burns off (disappears) this indicates that the aluminum has reached the correct temperature for annealing. I used a standard white candle, with no coloring or perfume. As I heated the aluminum, the soot actually disappears just like watching a fogged up window clear from your defroster. This is the simplest way to explain the change. If you continue to overhead the aluminum it will start getting a crinkled appearance to the aluminum (not good).

I suggest you drill your holes before annealing. As the aluminum gets very soft, the aluminum will smear and even twist if the bit grabs it. Your bit will also load up with aluminum.

Also do any kerfing before annealing.

Always use Stainless Steel screws that will have any exposure to the elements as you will have the dreaded red streaks of rust if you don't.

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Postby cracker39 » Tue Jun 13, 2006 10:39 am

I'm planning on getting a metal punch from HF and punching the holes, not drilling. That's another $30 for the punch, but it will save lots of time and make cleaner holes.

Stainless screws will probably cost almost as much as my aluminum. Let's see...about 60', screws 5" apart on the average...hmmmmmm...about 160 screws oughtta do it.
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Postby madjack » Tue Jun 13, 2006 10:57 am

Dale...you've got it right and Bandit has it right...give ya both a ceegar :thumbsup: ...do y'all have a Fastenall in your area...darn good proces on those SS screws...check their site locator if unsure, 'cause they have lotssa storefronts...

...for painting, you will wanna scuff up the Al...there are primers and paint adhesion products specific to AL...ask your local paint supplier what they have/use

...only other thing I would add is to pracatice...the few bucks spent onna sacrificial piece of trim is worth it....uh yeah, keep that flame moving and preheat as you go...a propane torch with a fairly large tip or a speader tip(maybe) is really needed...unles you have a MAPP torch or such...I used one of those HF pistol grip torches...has a fairly large tip and the pisto grip is easier on your wrist...
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Postby cracker39 » Tue Jun 13, 2006 12:34 pm

Thanks, Jack. I two Fastenal stores in our yellow pages. I'll check with them for SS screws.
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Postby cracker39 » Tue Jun 13, 2006 12:40 pm

As I want my trim to be white, Can you buy white aluminum screws? Is there such a thing as screws made of aluminum? Our local surplus building supply sells screws in bulk by the lb. Most are hex head type. They have some that I think are aluminum. Don't know if they have round head or not. I can check with them to see what they have. I can use hex head, but prefer the look of round head on flat aluminum trim.
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Postby Bandit » Tue Jun 13, 2006 1:30 pm

Be very careful with aluminum screws. You must pre-drill the full depth of the hole and not have the hole too tight that it spins the head off and not too loose that it does not seat properly and hold tight.
Some stainless steel screws will also spin off very easily.
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Postby cracker39 » Tue Jun 13, 2006 2:40 pm

Bandit, that's what I was afraid I'd hear about aluminum screws. But, I didn't know that stainless steel was that soft.
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Postby Bandit » Tue Jun 13, 2006 10:13 pm

It is not that they are soft, but brittle. It has to do with the grade of stainless. Not all stainless steel is rust proof, I believe it has to do with the nickel content.
I've purchase some SS screws that would strip the wood out and I've purchased others that once the screw is seated, if you don't stop, it will snap the head off. Be patient and pre-drill and you should have no problems.
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