Which steel bends easily?
 

I know we have a few machinists/metal fabricators here, so I'm hoping that someone will have some good advice on this: I'm working on a project where I need to bend short pieces of 3mm steel rod to a 3mm inner radius. I have been using drill rod so far, but it is a bit too hard and "springy" to get a nice 90 degree bend with a defined radius. Is there any other material than drill rod that would work better? The problem is that it needs to have a smooth finish (not necessarily ground though), and of course, it also need to be metric or a close equivalent.

Can we have more info? There are hundreds if not thousands.. how durable does it need to be? Will other metals be touching it (corrosion factor)? Does it need to be conductive? What is the normal temperature will it be exposed to? How are you bending it (pliers, pipe tools, sheet metal benders...?)

This is a lanyard loop for a pistol, it's a rectangular shape made out of 3mm rod and with 3mm radii. The strength is not critical, but it needs to bend easily and cleanly, and it needs a fairly nice surface so it can be blued without excessive prep. The tolerances are not extremely critical, maybe within 5/1000 or so.

I'm using a die do form it cold, and I can't really heat it. I have already tried to anneal the drill rod, it did make some difference but not much. I think something like 1018 cold finish round would work, but I can't find it in metric dimensions.

I have a piece or two...
 

Drill rod is too hard...I have some 10 series 3MM rod, it will work great for your lanyard loop... send me your address, (send to: gctomeks@msn.com ) and I'll send you a small length.. all I have left is some short pieces .1177" to .1180" dia. ... Some is cold rolled, some is drawn wire, so it, the wire, will have a slight surface hardening, not an issue for your radius... it's as close as your ever going to get! Believe me, I've chased this dog to death!...;)...best to you, til...lat'r...GT ...;)

gads.. has a be blue-able? I know a lot about metals but no clue about blueing.. I was originally thinking brass or a bronze but they won't finish.. seriously try the hanger but do a test blue first.. might come out a completely different value then the rest of the project. Find a gun that has a similar lanyard and look on numrich (gunpartscorp.com). Sorry I couldn't help more.. fof once I thought I could answer something on here! lol

it's a rectangular shape...

You might have a great deal of trouble with squared corners whatever you are using. They are quite difficult to square up..they tend to round over instead.

What kind of lanyard loop is this?

that's different...
 

Good catch Jerry! ....;)... I'd cut and sand it out of a piece of cold rolled 1008 to 1018 flat stock... only have to control one edge.... ;)....best to all, til...lat'r...GT

Yep, the rod tends to bend in the wrong places. This is for the P.38 (the loop has the same basic shape as paper staple), and I'm having a hard time getting the straight sections straight. I have made a pretty tight and sturdy die, where the head has a cap that I can tighten down to hold the rod. This die is then pressed into a tight fixture, which folds the legs of the loop. I don't have any pictures, but if you imagine the die and the rod as a "T" shape that is pressed into a square hole, you'll get the idea.

I have made the tool to pretty tight tolerances, but it's still difficult to get the shape right due to the small size. There's simply not enough rod for the die to hold on to when I bend it, and work hardening probably adds to the problem as well. I suspect that the original loops were formed hot, but I can't really do that as it would also weaken the die.

The only solution I can see is to find a softer rod that bends easily and cleanly, and doesn't spring back as much as the drill rod does. The ends need to be turned down before I bend it so the material needs to be fairly machinable, but the strength shouldn't be a problem at all.

You have mail.

The drill rod is hard alright, hard, springy and everything else that makes it difficult to bend. :banghead:

The cut length is about 1 1/4" so I don't need much, if I get enough for 2-3 attempts I'll be more than happy. This might save a lot of research so your help is greatly appreciated!

A lanyard loop for a P-38...Have you asked on any of the P-38 forums if anyone has one they would part with??? You would be surprised at what members of these specialized niche forums (like ours) have squirreled away... ;)

It's not for myself, I'm actually doing it on request from a P.38 forum member. It seems like there's many pistols with missing loops, and not enough loops available.

I'm actually on the lookout for a Mauser C96 with an OEM lanyard ring to measure...Neither of mine has one, and I don't know the diameter or wire gauge...And, like you say, most seem to be missing the original loops and keyrings have been substituted (now or in the past)... :(

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!

If I were doing this I might attempt it this way..Fashion a bar of steel with sharp edges and wrap your wire around it under as much tension as you can manage.. hammering the wire at the flats and corners with a lead or plastic mallet. Then cut your staple out with a rotary tool like a Dremel. Might take some adjustment on the size of the steel bar to get the size accurate enough but once it's perfected it would make a lot of staples quickly.

If I remember correctly..many times these types of wire bends are cut at the undersides of the corner bends. Removing some small amount of steel there allows for a clean bend.

When you get a staple you like it is very simple to fire blue it. Lay it on a fire brick and scan a plumbers torch over it..slowly feathering around it untill it magically turns to a straw color..take your torch away at this point as it will continue to heat and likely turn a beautiful fire blue. If you want a dark blue to black keep your torch on untill you see the fire blue..take it off and it will be done. Do NOT quench it in anything. Let it cool and oil it.

I have even fire blued relatively large parts like buttplates..

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.

This project would be much less difficult if I could bend it first and then cut the legs to the correct length. The reason why I can't do that is that the ends need to be turned down to 2.5mm, which forms a shoulder that acts as a stop when you tap it into the frame. This means that I have to cut the rod to the exact length, turn both ends and center it carefully in the tool in order for the legs to come out the same length.

I have Walther's original drawing for this part and the cut length is 3mm longer than what I have found necessary, so it's quite possible that the factory had a way of trimming and forming the ends after the rod was bent.

If this small step on the ends of each leg is not extremely critical you might play with a Dremel sanding drum. I have found you can sand round rod like you need with the Dremel..clamp vice grips as a stop and let the drum naturally rotate around the wire tip from centrifical force and with a little practice I bet you could get a good enough trim. Dremel makes a very fine sanding drum that wouldn't take off too much per rotation. Worth a try..of course I am Bubba personified..I use a one half inch hand drill for a lathe.

You might want to try welding rods

I have actually done something very similar in the past, but with a file. I taped the loop where the step needed to be, and clamped it in the vise with the legs sticking up and flush with the tape. Then I used a "safe side" file to file down the ends, using the vise jaws as a guide. I found that filing them to a square first was the best way to stay on center, and once I had them squared to the correct dimension I rounded them off. It was actually a surprisingly quick and accurate method. I was planning to use Loctite, but I tapped it in for a dry fit and it stuck so well that I left it like that. Anyway, it seems like I'm going to make quite a few of these loops, so hand filing is not really an option.

And there's nothing wrong with using a power drill for a lathe, it's the quickest and easiest way to shave stubborn pins a tad and it's also the perfect way to reshape buggered screw heads. The easier, the better. ;)

I have already looked for welding rod, but haven't found any in metric dimensions yet. I might talk to my buddies in Sweden and see if they can find some for me. I have used it for other projects in the past and it's pretty nice to work with, the only problem is that some types contains too much nickel to blue well.