What's new
What's new

annealing aluminum with a plumbers torch

scphantm

Cast Iron
Joined
Jul 15, 2004
Location
Pittsburgh, PA
I need to put some 90 degree bends in some home depot aluminum flat bar. i know if i try without annealing it first, it will crack. but currently my shop is sitting in a storage unit 200 miles away. Will a plane old plumbers torch get hot enough to anneal this stuff for bending?

I was going to use the old trick of mark it up with a sharpie and heat it till the sharpie burns off. Just don't know if i have enough heat.

butane in the plumbers torch maybe?
 
what more do you need? i don't know what alloy Home Depot sells, its the 1/8th inch stuff, mostly 1/2 wide. Don't know what else to tell you. Sorry.
 
Home Depot aluminum is going to be 6061 or 6063 most likely at T651 hardness. With 1/8th flat bar you should be able to bend 90 deg cold without cracking - I've done it many times. 1/4" you would probably crack if trying for a short radius. 1/8 might crack if your bend line is along the extruded length. If you anneal it you will lose around 60% of the strength, if that matters. It cannot be re-hardened effectively in the field. If it is anodized, the anodizing will crack for sure whether annealed or not - you will see that on the outside radius but it will not affect strength noticeably.
 
Im just building some brackets for my bicycle. Im on location for work and had to put my shop in storage till this jobs done. Ive tried cold bending this stuff before and got to about 80 degrees before the outside shattered. Maybe it was just that batch. but i will give it a shot.

But, if anyone knows of a small fab shop, or home shop with skills, within stones throw of downtown Harrisburg, i would gladly farm it out. I would much rather have this thing welded rather than me bolting it together but all the boys around here are scrappers, no fab shops. except one, but they do bridges so i couldn't even get the secretary to talk to me.

but, in the mean time, i will see what i can get it to do.
 
It totally depends how sharp you're aiming for the corner to be. A gradual 90 degree bend done on a hossfeld? No problem. I've bent heaps of 3/8" thick 6061 bar with no cracks without annealing it first. It's a different story if you're going to stick the piece in a vise and mash it with a hammer. I wouldn't put good odds on the mystery-metal + vise + hammer plan but annealing it first will at least improve your chances.

A mapp gas torch will get us to 5300*F, I don't think any aluminum alloys require more than 1000*F. A mapp torch should have no problem heating a small piece of aluminum to the temperature you need.
 
Hey guys...you are making it much too complicated. He asked a simple question, with a reasonable solution. The Sharpie marking works quite well for the bend that he is wanting. Same as using an oxy-acet rig to apply a layer of carbon soot to the surface, and then heat it to burn it off.

Lee (the saw guy)
 
I've never tried the sharpie trick but I have bent (or straightened) aluminum a few times by heating it until a small piece of white pine just leaves a char mark when rubbed. I learned this from an old time welder who used to have a shop near a friend's house.
 
It's 1/8 X 1/2 for a quickie bike rack. Heat the bend line until you think it's "real hot" then bend it in a vise. Works 99% of the time. If not just heat it until it's really real hot and try again. You'll get the hang of it real quick..............Bob
 
I've bent 2024 T6 with a Burnz-O-Matic torch. Heat, quench, bend.

For a hanging bracket for a bike, I'd suggest going to Home Depot and getting a couple of closet pole brackets.
 
Old-time, rough and ready temperature indicator for annealing aluminium - rub a bar of soap on it and heat until the soap turns brown. It works for me.

George
 
Just try the soap on a bit of scrap first. My mum when i was a kid use to be a Avon lady and one of our bars of soap did not work :-( My piece i had spent about 2 hours cutting out by hand with a fretsaw paid the ultimate price.

Of cause every bar - time i have used the trick since + tried on scrap first i have yet to find another bar that did not work :-(
 
Oldster has it right: soot the aluminum with a candle and bend it when the soot burns off. I haven't tried the soap method,though it likely works,too.
 
seeing as aluminium melts at 700 celcius or so, even a std cooker hot plate will get hot enough to anneal it.
 
Propane torch gets plenty hot. Sharpie or soot black then just heat enough to burn most off. Don't try to burn it clean or you'll end up with a puddle. DO NOT bend teh work when hot. Aluminum (especially 6061) is hot short, which means it drastically loses strength when hot. It will crumble like a warm cookie if you bend it without letting it cool back down. You can quench in water directly from the anneal without hardening or affecting it.
 
Sorry to dig up an old thread, just wanted to post that teh Sharpie trick works like a charm. Cracked some 1/8" sheet trying to bend it so jumped on the interwebs and found this post. Gave it a try and worked like a charm.
 
Rub with white soap bar, heat till it blackens the old fashioned way!
Mark
Sorry limy,and others poor reading skills must be the CoViD
 
Annealing with a torch may or may not work. The trick to hot bend aluminum is not to overheat it because there is no color change to guide us. An old timer's trick is to take a small piece of Eastern white pine and rub it on the aluminum as you heat it. When it leaves a black smear the aluminum is at the right temperature for safe bending. I've straightened a lot of stuff that way, especially when I rode off-road motorcycles. Straightening bent levers and pedals often got the bike back in service while waiting for replacement parts to come in. After replacing the parts I usually kept the straightened parts for emergency spares.
 








 
Back
Top