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-   -   Bending Aluminum. Heat? No Heat? (https://www.rcuniverse.com/forum/clubhouse-190/11374982-bending-aluminum-heat-no-heat.html)

bugsymalone 01-18-2013 10:28 AM

Bending Aluminum. Heat? No Heat?
 
I need to make a couple of 90 degree bends in some 1/8" x 3/4" aluminum stock I purchased at an OSH hardware store, so I'm not sure exactly what type aluminum it is. It's not anodized though, as I have worked with it before to fabricate the two sets of gear necessary for a float plane I built. It's the identical stock. I need to make two simple horizontal struts to restrict my gear from splaying out for my not so perfect landings. These struts will look something like this: l______________l. About 17" wide with 1" vertical ends. All my bends in my original gear were less than 90 degrees, but these struts require two right angles. I was wondering if I should heat the area of the bend first prior to bending. Any thoughts? Thanks in advance for your advice.

hugger-4641 01-18-2013 10:43 AM

RE: Bending Aluminum. Heat? No Heat?
 
You need to use something as a guide to give your bend a small radius. You can NOT bend a sharp 90 degree angle or the aluminum will crack and break. Heat will help, but it will also weaken the metal. Put one end of the aluminum in a vise and use a piece of 1/4" black pipe or a 1/2 bolt to bend the aluminum around to achieve your angle without trying to force the metal into a sharp 90degree bend.

vicman 01-18-2013 06:28 PM

RE: Bending Aluminum. Heat? No Heat?
 
The grade and T number are very important when forming aluminium.
If it is 6061 t6 which is very common you won't be succesful going past 45 degrees. It will crack.
To solve the problem you want to anneal it. This can be done with a propane torch, get it up to about 600 degrees and let it cool slowly. Do your bending and then re-harden it.
Again with your torch heat it up around 900 carefull not to melt it and quench it in water.

This process is not scientific/metalurgically perfect but will work for the shop and little airplanes.

hugger-4641 01-18-2013 08:25 PM

RE: Bending Aluminum. Heat? No Heat?
 
Even annealing will not stop 1/8" thick 6061 from cracking if he bends it too sharp, but annealing will help if he does it properly and follows up with re-heat treat and quench as you describe. If he makes his bends while the metal is still about 600 degrees, he might achieve a sharper angle, but I've done this many times and unless you use a heat stick or some kind of temperature sensing device, it is very dificult to get the right temperature to find the bending moment without going too far and getting grain seperation and tears, which he may or may not easily see, but will probably show up nicely at the first hard landing.

HighPlains 01-18-2013 10:31 PM

RE: Bending Aluminum. Heat? No Heat?
 
You are more likely to win the Lotto than find 6061 at an OSH store.

combatpigg 01-18-2013 10:59 PM

RE: Bending Aluminum. Heat? No Heat?
 
Try working with "road sign" aluminum. Very tough stuff....might even be strong enough for a 3 to 4 pound plane.
For making 1/8" or thicker 6061 [medium hardness] workable, all I've ever done is cover it with soot, then lick the flame over the soot until it gets burned off. Let it cool gradually.

bugsymalone 01-18-2013 11:00 PM

RE: Bending Aluminum. Heat? No Heat?
 
Hmmmm...these are all good suggestions. I swung by OSH today and found out who the supplier is. The aluminum is by "MD Building Products". They call it a "Mill" grade, but that's was all I could learn from their website. I think I will give them a call on Monday. See if they can give me any advice regarding bending this specific grade of aluminum. When bending out my main gear, I was successful bending around 50 or 60 degree bends cold. No cracking. I like the advice of bending around a 1/2" rod or bolt. I think I'll be ok and will let you know how I fare. Thanks for the advice.

STUKA BARRY 01-19-2013 01:25 PM

RE: Bending Aluminum. Heat? No Heat?
 
You also want to bend the metal against the grain for less chance of cracking, bending metal with the grain is a sure way of it cracking. Fortunately for you, 6061 is the cheapest garbage metal which allows it to be welded. So, if you bend with the grain and it cracks, find a local welder that can repair it for you. It wont be pretty, but it will be functional. 2024 is a better metal for gear. 7075 is best, but much harder to bend.

hugger-4641 01-19-2013 04:20 PM

RE: Bending Aluminum. Heat? No Heat?
 
Most likely the stock he's using is extruded 6061, probably T6, T6511, or T76511 if it was intended to have some corrosion resistance. Possibly it is a 4xxx or 2011(K211) alloy, but this alloy is not commonly extruded in a rectangle, usually round screw machine stock. 2024 and 7075 are more expensive alloys and not usually sold for "mill stock" unless it was some odd inventory a distributor managed to sell off to a hardware store. Unless he knows someone with a spectrometer, the only way he is likely to find out what alloy it is will be to rifle though the store's inventory and find a piece with the stencil. That's assuming it was made here in the states and not shipped over from China.

I happen to have some short pieces of 1/8" x 1" 2024 T351. If you don't have any luck with the stock you are using, PM me.<br type="_moz" />

jester_s1 01-20-2013 07:58 PM

RE: Bending Aluminum. Heat? No Heat?
 
You guys giving heat treating advice would do well to actually learn about heat treating before giving the advice.

IF the alloy is actually 6061 that is a heat treatable aluminum. It will respond to heat treating if the user has good temperature controls and can give it the soak time at heat that it needs and quench and temper at the right temperature. Without that, there's no way you'll get consistent hardness and the likelihood is pretty high that you'll burn the aluminum which renders the whole piece useless.

Most of the hardness and stiffness you get in a piece of rolled or extruded aluminum comes from the working process itself. If you do manage to anneal a piece of rolled aluminum, you'll have a heck of a time getting the same properties back into it without pouring it into a block and rolling it out again.

It is possible to work aluminum (at least all the common alloys) around 500 degrees to soften it up a bit. That's more about making it easier to work than preventing cracks though. Making a nice gentle bend is the key to keeping the strength in the material. If you pick a big enough radius, you can go 360 degrees if you want to with no damage whatsoever.

hugger-4641 01-20-2013 09:05 PM

RE: Bending Aluminum. Heat? No Heat?
 
I don't know your background, but if you are referring to me, I've worked in aluminum extrusion of hard and soft alloy rod and bar for Kaiser for over 13 years. I've run and maintained every piece of equipment from the extrusion press itself, the heat treat furnaces, the anneal/artificial age furnace, stretchers, draw benches, and roll straigteners. I also maintained and calibrated the combustion train and the thermocouple array on the heat treat and anneal furnaces. I also programmed and made modifications to the heat cycles on these furnaces. While I don't claim to be a metalurgist myself, I was trained by one of the best in the industry, a man name Roy Coats, so unless you are a metalurgist, you will not likely be educating me on aluminum extrusion or how to heat treat or anneal it.

That said, 6061 extrusion is most commonly heat treated between 900 and 1200 degress and then quenched with water as Vicman described.

Annealing is accomplished as much by the slow cool down as it is the temperature it is heated to, but a proper anneal actually has a two stage heat cycle, first a soak at high temperature, depending on alloy, usually 600 to 900 degrees. Then a slow, controlled ramp down to a stabilizing soak at a lower temp, usually around 300 degrees.

Vicman's advice was not accurate to the "T" as he admitted, but it was close enough. You are correct that cold worked stock can not be returned to its original temper by heat treating alone but must be re-worked, which is why I did not advise heating it, but rather bending over some other object to get a radius if he could. But if he must heat it to get the radius he needs, it can help prevent cracking, and the metal can be strengthened to some degree by re-heat treating.

vicman 01-21-2013 04:24 AM

RE: Bending Aluminum. Heat? No Heat?
 
Thanks for the nice words Hugger. ;)

hugger-4641 01-21-2013 08:36 AM

RE: Bending Aluminum. Heat? No Heat?
 
No problem. We're all just trying to help here, Jester included. I don't have a problem being corrected when I am wrong, ignorant, or un-informed about something. I just don't happen to be a novice when it comes to aluminum. I also don't try to give everyone a metalurgy class when the subject comes up. I just try to give enough information to help with the task at hand until the need arrises for more details.
That's the great thing about these forums; everyone here is not an engineer or ex-fighter pilot, we all bring an area of expertise to the table along with a wide range of general skills and knowledge.http://www.rcuniverse.com/forum/js/f...wink_smile.gif

vicman 01-21-2013 02:41 PM

RE: Bending Aluminum. Heat? No Heat?
 
I'm no metalurgist either but I have been in industry for close to 30 years and done a ton of heat treating on a huge range of materials, al included.
It was reasuring to know my empirical knowlege was backed up by another with the same experience.

jester_s1 01-21-2013 08:30 PM

RE: Bending Aluminum. Heat? No Heat?
 
You came off like you knew what you were talking about Hugger, essentially telling him to skip the uncontrolled heat treat process and just bend it over a gentle radius (at least that's how I took you). I was more countering vicman who's telling a guy to do a process that does require some fairly tight temperature controls who likely only has a propane torch to do it with in his garage. I'm sure you know working in the industry that he's far more likely to mess up his gear than he is to get it right. I wasn't trying to give a metallurgy lesson just to look smart, but rather to back up what I was saying.
I've never worked in the industry you have, just did some hobby blacksmithing and knifemaking in college. It's good to meet you and I suppose if I ever have a conundrum with a piece of aluminum I'll know who to shoot a PM to!

vicman 01-22-2013 04:16 AM

RE: Bending Aluminum. Heat? No Heat?
 

I was more countering vicman who's telling a guy to do a process that does require some fairly tight temperature controls who likely only has a propane torch to do it with in his garage.
Shame on you Jester.[:o]
Comments like that mess up good threads.

My process was for the guy who likely only has a propane torch in his garage.

hugger-4641 01-22-2013 01:19 PM

RE: Bending Aluminum. Heat? No Heat?
 
No problem Jester, PM me anytime, be glad to help anyway I can.http://www.rcuniverse.com/forum/js/f...ades_smile.gif


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