How do I bend aluminum without it fracturing?

lerner said:
So this is the info I'm going to rely on:
1) I wont heat the Al anywhere near melting. Just enough to decrease the min. bend radius (i.e. increase malleability?). Butane lighter or gas stove for couple minutes.
2) One expert said the clamp is probably 6061. Another expert said 7075. Both recommended against bending.
3) Correct me if I'm wrong, but the clamp definately doesnt compare to Al sheet-metal.
4) there is no glue/epoxy/adhesive as strong as the Al itself; and Al cant easily be soldered/brazed.
5) The discussion is rather academic now; Any method will be hit-or-miss; I will probably ruin this clamp, buy another, ruin with different method...

What I'm still interested in is this:
the terms O condition (soft), T3 state, W condition (unstable)...
What scale or series are they members of that I can google?
Click to expand...

1) the butane lighter isn't a good method, the heat will not be even. If you have an oven that will hit 500F, that would be better.
2) It is unlikely that the clamp is 7075. Not a common alloy outside of aerospace. 6061 is a pretty common alloy for all sorts of things and would be my best guess as to what your clamps are. And I recommend against trying to bend it as well.
3) Talking alloy, not form. what he said about bending aluminum holds no matter what the form.
4) So, does it NEED to be as strong as aluminum? All you are doing is holding a knife. That doesn't take ultimate strength by a long shot. Remember, in clamping, you are pressing down on whatever you bond to the clamp, so there is little stress on the bond itself. The stress won't be tensile at all and there will be little peel stress either.
5) True.

O and W are not a scale. They are metallurgical heat treat terms. They describe the properties a metal has when it has a specific crystal structure. The crystal structure is what you are modifying when you heat treat.
Google
aluminum "heat treat"
and see what you get.
 
7075 is a very common grade. It is used extensively for thin structural extrusions in car ports, summer rooms etc. It is also heavily used for window frames, door frames and sliding glass doors. It is usually coated to prevent oxidization. I used to process tons of it when working at the scrap yard. Most of it came from companies that specialized in door and window frames. The clamps are probably 6061 as it is usually used for thicker structures like conduit or square tubing. I had forgotten that 6061 was generally used for thicker walled components than 7075 is. We had one company that sent us a lot of 7075 that they used for small gears and bicycle sprockets.
http://www.bikeparts.com/productinfo/FBM-Race-BM-43t-7075-Sprocket-332-48098-96164.html
 
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For reference, what I finally did is grind out a wide "tooth" on the Lansky clamp end:
With a file, (carefully) grind two parallel recesses about 1mm apart. Remove more stock on each side to develop the tooth in the middle.
The tooth grips like a claw into the previously dremeled grooves on each side of the knife's backbone.

I can tighten the clamp with a screwdriver to grip the knife extremely tight, and the clamp hasnt deformed any (yet).
 
lerner said:
For reference, what I finally did is grind out a wide "tooth" on the Lansky clamp end:
With a file, (carefully) grind two parallel recesses about 1mm apart. Remove more stock on each side to develop the tooth in the middle.
The tooth grips like a claw into the previously dremeled grooves on each side of the knife's backbone.

I can tighten the clamp with a screwdriver to grip the knife extremely tight, and the clamp hasnt deformed any (yet).
Click to expand...

Good solution to the problem.:thumbup:
 
A lot of good suggestions, but I add one more 'Old Book" trick.

Get a Black Sharpe and mark the area you wish to bend.
Heat the material slowly end to end of the marked area (and a little past).
As soon as the mark turn semi-white, it's ready to bend - but be quick.
If you don't get it the first time, you can add a just a little heat.
(The problem is that you can only use the trick once.)
Caution: Once you hit the white, stop. beyond that point the material will melt.
Have fun
 
The best grip-assist I've found, used with the Lansky (or Gatco) clamp, is a piece of 400+ grit wet/dry sandpaper folded over the spine of the knife, with the PAPER BACKING against the blade (won't scratch) and the grit side facing the clamp faces. Works great, even when wet.
 
knarfeng said:
How hot you would need to get it depends on the alloy. But, if it is a heat treated grade, if you heat it enough to bend it you will ruin the temper. Then it won't hold the knife properly anyway. Best guess at a generic temperature for being able to bend is ~500F. But I really don't recommend this.

I think you would be better off modifying the grip by bonding something to the grip ends. You might try getting some aluminum shim stock or other thin metal, cutting it to shape, then bonding it to the ends of the clamp with high strength epoxy adhesive as sold in the local hardware. Much more likely to succeed.
Click to expand...

This. Much more reasonable.

When I've had to bend Al in the lab, I've done it slowly around large-radius cylinders of a harder metal. Never tried it around something small like a nail.
 
The "tooth" could also be make from a brass rod that is imbedded into the clamp, held in place by epoxy.


Leadfoot
 
Yeah, it's a bad idea to try heating and bending thin aluminum when you don't know much about the process. And if you think you can heat aluminum enough to bend it with a butane cigarette lighter you don't know much about it. Aluminum conducts heat like a motha'. A propane torch at minimum is necessary, and for thicker stuff an oxygen/acetylene torch and/or an oven are necessary. The cracking that occurs when the aluminum is bent past its minimum bend radius doesn't have to do with heat, it happens because the maximum elongation spec is exceeded on one side (external radius of the bend). If you do happen to get a successful bend, then you need to heat treat again to bring back the hardness or it won't be as strong as it was. The grooving idea is much better than trying to bend the Lansky clamp.
 
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