Quote:
Originally Posted by ithacaartist
I'm having trouble understanding why annealed drill rod, or whatever alloy, is still too stiff to form. When annealing steel, the longer it takes to cool down from cherry red to working temp., the closer it will be to dead soft. Try sticking the hot piece into a metal container of hot ashes, and allow the whole deal to cool overnight. This will act as insulation and buffer to ensure that the cooling will take as long as possible.
Also, have you considered doing the bending hot? It would be a lot easier, and if you're heating the piece to anneal, anyway, why not bend 'er when she's most plastic?
As far as the material's bending where you don't want it bent...
The points of contact opposite the internal apex of the right angle, on the outside edge of the piece, must be pretty close to the point of contact for the inside mandrel/pin, and it would help prevent the formation of a "dent" by each of these contacts if they were smooth-could even be flat. If you simply set up a square, inside corner and pushed/tapped the correct point along the length of rod straight into it with the tip of a screwdriver (Dress/grind the tip to remove the sq. corners, to the internal radius you desire.), that should do it for sure, if you're doing it hot. If cold, there will be "springback", so you'll need to make the corner more acute than dead square--this determined by how much the material of choice springs back after bending forces are removed, thus a little experimentation is necessary to determine the degree of acuteness necessary in order for the formed piece to be square after you let off bending and it springs back.
I hope this is clear. Sometimes difficult to put everyday activities and procedures into words! ...Try writing a set of instructions for tying a shoelace into a bow knot!
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I think I follow what you say, and I think that the bending tool adresses the issues except for the "overbending" to allow for some springback. That part is not much of an issue though, it springs back less than 1/2 mm total (i.e. center to center) so it's easy to get the legs aligned by simply squeezing them slightly in the vise.
The section connecting the legs is the hardest part, it should be straight but ends up slightly bent. The tool has a screwed on cap that clamps it down in a 3mm groove (kind of the same way handle bars are attached on bicycles), and I have also inserted hardened dowels for the wire to bend over. In theory, the connecting section shouldn't bend, but it still does. It could be that the force required to bend the rod is enough for the cap screws to stretch a bit. This is one of the reasons why I don't want to heat it, there wasn't room so the screws are pretty small, and if I heat the tool they might just snap. This is a typical case where pictures will tell you more than a thousand words, so I'll se if I can snap a few so you can see what the tool looks like.
The "screwdriver method" works well (I use it every now and then), but there needs to be a neat, 3mm radius so I would have to come up with a rounded tool for it. Hitting the right spot with a screwdriver is fairly easy, but I'm afraid that it would be challenging to get it to bend exactly where it needs to bend if you use a rounded tool. I might try that if my contraption doesn't work.
As far as annealing the wire, I have heated it and stuck it in sand. I might try and heat the sand and see if it works better. However, it would be great if I can find a material that works without any prep, so we'll see what GT comes up with.