Question on bending aluminum....

[Snaggletooth]

Ok.... I don't know nutting about this one. I've had good luck bending and shaping thin aluminum sheet before but I've moved in to the heavier stuff on another project.

 

I bought some 1/8" x 2" aluminum strap today for making some brackets. I need to put some 90 degree bends across the width of this stuff. With the 1/8" thickness am I going to be concerned about stress or cracking at the bends making that sharp of a bend?

 

No real weight will be on the bracket after mounting but don't want to weaken it in the process.

 

Mike

[Redneck]

I don't think you will need to worry about cracking during the bend but anytime you bend any metal you will create stress. The more radius you can put in the bend the stronger it will be.

[kevin-vic-b.c.]

I don't think you will need to worry about cracking during the bend but anytime you bend any metal you will create stress. The more radius you can put in the bend the stronger it will be.

 

 

I do not know anything about bending the Aluminium either but yes logic says a long radius is best.

[playboy]

I did that making some extensions for a spot mirror on my Truck the wind and vibration was to much for it and it broke at the bend and I watched the mirror explode going down the hwy. The rest of the day was pretty much a water haul.

[Bubber]

For what it is worth, when you bend the Aluminum you are going to work harden it, at least with most shapes and chemistries. Bent the piece in your vise and sandwich it between two pieces of wood. Radius the edge of the wood so that there is no sharp edge transferred to the Aluminum.

 

I haven't tried this but place a bolt cross wise at the bend location so that the strap rolls over the radius of the bolt when bending.

So the sandwich should be wood in back then strap then bolt then wood.

You should get a nice radius and and that will transfer stresses better than a sharp 90 degree bend.

That's my 2 cents worth.

 

Good luck

[Snaggletooth]

Gotcha.

 

I was thinking about doing the bend with a brake (that's why I asked) but it sounds like a better idea to bend it over a round pin for reduce the stress a bit. Don't have a lot of room for a big radius bend but a 3/8 pin should help.

 

Thanks guys.

 

Mike

[skydoc_17]

Hey Mike,

Here is the method I use to bend Aluminum. Place the Aluminum strap in a vise. I use the small bottled MAPP Gas Cylinders, because you can control the heat better. (It's WAY to easy to overheat the Aluminum with an Oxy-Acetylene rig) With the strap in the vise where you want the bent to happen, slowly "wave" the MAPP gas torch back and forth at the junction where the vise and the Aluminum come together. With your free hand, apply some pressure to the Aluminum Strap part sticking out of the vise. (Caution, strap may be HOT! use a piece of scrap wood for this) DO NOT force the Aluminum over to the 90 degree angle, just put steady pressure on the strap, and let the heat "move" the metal.

There is a bit of a "technique" to this so you may want to try it a few times on some rem pieces, before you try the real strap. What you are looking for is enough heat to "move" the metal to the 90 degree angle, but do not overheat. The other thing you are looking for is, don't bend the metal BEFORE it gets hot enough, this is why I use the steady pressure method. The metal will "let you know" when it is hot enough by starting to bend.

If you have questions Mike, feel free to PM me.

Earl

[dingy]

It really depends on loading and width of the piece at the bend.

 

Previous occupation I was designing metal enclosures made out of 1/8" 6061 sheet. Typically, after part was punched out using a Strippet turret punch, the pieces would be formed on a somewhat standard 10' hyd. brake press. Typically used a 1/16" inner radius die set. If you are just going to do a single bend, material length is easy to calculate. But if you need more than 1 bend, and you are doing sharp bends, then you need to do a bend allowance calculation. The material stretches slightly at each bend, this is a critical calculation when a corner panel is done. I had a couple that had 8 bends in them, corners, offsets for doors, and insulation pockets. with each bend growing the overall length it was interesting getting the last bend worked out so there was the required length for it.

 

Excel sheet I made up to help with calculations attached. I put a few values in for 3 legs, to help see what it does.

 

Gary

[van avery]

Just a quick safety note. I know your bending the aluminum. But don't use a grinder on aluminum and then go back to grinding steel. The aluminum will build up in the "pockets" of the grinding wheel and when you use it on steel it will get hot and the aluminum expands and some grinding wheels have been know to break apart.

[Flyinfool]

It all depends on the alloy and the temper of your aluminum.

If you are getting the Aluminum at the hardware store odds are it is 6063-T651.

If so then the general rule of thumb would be to use an inside bend radius equal to 3 times the material thickness.

[bj66]

I used to work with alum. fairly regularly. It all depends on the number of alloy you are using. 6061 is aircraft aluminum. I used to work for a company that makes fans. When I'd roll the alum. for the housings its tensile strength would almost double every pass through the roll. 6061 is really hard to form. We would use a rosebud on a cutting torch and heat it really hot before trying to bend in a press brake. I cracked as much as I formed seems like. 5052 alloy is much more forgiving, easier to work with. Most barstock you get is 6061. When we would try to form straps say 1" wide by 1/8" thick we would shear strips of 5052 rather than try and form barstock in 6061 alloy. You would get the straps to about 80 degrees and just about have it then the stuff would crack, even with heat.

 

Id agree with Jeff, the bend radius is key, Our company wanted a tight radius, like some of the steel we were bending. The aluminum wouldnt hold up to that tight of radius.

 

One other thing, working in a fabrication plant, we were constantly using fresh steel that was pickled and oiled. Our leather gloves always had plenty of oil on them from handling that stuff all the time. When heating the aluminum to bend it, we'd test the amount of heat the alum had absorbed by quickly running our oily gloved finger over it. The smear from our glove would start to smoke before the aluminum gets too hot. That became a good tell tale sign that it was ready to bend.

Edited May 11, 2012 by bj66

[Flyinfool]

6061 also has another neat property. You can get it as 6061-T0 and it will do a nice tight bend with no cracking or you can get it in a -T4 temper for something in between. It can then be heat treated to the T6 hardness to get the strength back. OR it will age harden all by its self. So if you want tight bends and the strength of 6061-T6 you have to have fresh -T0 or -T4 to work with. Be patient and it will age harden.

[Guest]

I do remember when we were making the fork deflectors using 6061 T6 we destroyed some pieces when we bent, on a brake, the top portion of the piece, to mate up under the driving light bracket. If I remember right, to get the proper angle to line up with the fork tubes we had to bend the tops to about 75 deg. A few pieces were bent beyond that point and at the 85-90 deg mark they either snapped or cracked. The more radius, the less chance of breakage.

[dfitzbiz]

This should be helpful http://www.wisetool.com/bendradius.htm

[ACE50]

I used to work with alum. fairly regularly. It all depends on the number of alloy you are using. 6061 is aircraft aluminum. I used to work for a company that makes fans. When I'd roll the alum. for the housings its tensile strength would almost double every pass through the roll. 6061 is really hard to form. We would use a rosebud on a cutting torch and heat it really hot before trying to bend in a press brake. I cracked as much as I formed seems like. 5052 alloy is much more forgiving, easier to work with. Most barstock you get is 6061.

 

We bend alum all the time but use 5052. 6061 if it is a flat part.

[FuzzyRSTD]

Use 1/8 " steel instead Snagggle. Go with a narrower strap than the aluminum, per-say 1" rather than 2" wide.

 

Fuzzy

[bj66]

We bend alum all the time but use 5052. 6061 if it is a flat part.

 

Our head of purchasing would get whatever he could get cheapest I think. I dont think he paid much attention to alloys. One time I had to put a 12 degree bend lengthwise down one side of a piece of 4 x 5 x 3/8 alum angle in 6061 that was about 3 feet long. So I heated the side that needed to be bent, and like a idiot I held on to the alum and stood right in front of it. All I heard was a big bang when I went to bend it. Suddenly I wasnt holding on to it, and I heard it hit the floor about 4 feet behind me. It broke the angle right in half, and threw the part I was holding on to over my head and into the aisle behind me. It happened so fast I never even saw it. Lucky I didnt get killed.