And what was the geometry of the punch?

It appears I accidentally made one of the forged carabiners I'm working on out of garage spring steel that I mixed up with some 6mm round mild steel I've been using.

I realised last night so I tried a poor man's anneal in ash overnight but I still can't drill it, especially because I only need about a 2mm hole through 4 or 5 mm of steel.

This one might be destined to be just a hook and not a carabiner with a wire clip in it, but it got me thinking: How small can you hot punch, and what shaped punch would you need? Or maybe the more important question is what steel should the punch be made out of to withstand heat in a small section?

Any ideas or previous experience?

Cheers,

Jono.

Hmmmmm. I think you could use S-7, it's a shock resistant steel with good heat resistance. I hear a lot about H-13 some of the modern anvils are being cast from it. I seem to recall it was used for small pins (Injection molding maybe?) of some sort being pretty common but for the life of me can't think what. Hopefully someone on the forum knows what I'm talking about.

Anyway, H-13 should work. . . I think.

Frosty The Lucky.

I might try drilling it with a (cheap) HSS bit just as it cools off a red heat. 

Another tip (if you aren’t doing this already) is to set the hook on a hot chunk of steel before you bury it in the ash — or better, sandwich it between two chunks. The greater thermal mass will slow the rate of heat loss, and might well be enough to get the piece soft.

Stefan Gotteswinter did a detailed video on this problem a few years ago, on his youtube. He has some good tips:

 

Well, that video covered just about everything i was going to say. One thing not mentioned though is the angle of the drill point. A 135° angle will cut harder material easier than a 118°. The flatter the point the better for hard material becuase it provides more of the cutting edge to be in contact with the material at the start. 

Take note of how much coolant was used to cut those holes. Like i said in another post you do not need much at all, if any most of the time. The deeper the hole the more you need it but it is mostly to lubricate the tool to keep the chip moving out of the hole. 

Punching the hole i would use a hole punch gizmo i can not for the life of me remember the name of. That way the punch can be as short as possible and not bend as easily when it gets hot from the material being punched. 

Second, or maybe at this point third using a big hunk of helper steel for annealing to hold the thermal mass. Also, you may have work hardened the area around your hole while drilling if you generated too much heat and it cooled off rapidly. It's easier to do with small steel, especially if you go too fast, too deep, or too hard, or if your bit is too dull. You can also burn up the drill bit, but that's not nearly as frustrating. 

If they're not burnt and are a little dull, you can also resharpen bits on a grinder. It takes a bit of practice and checking the angle when you start, but it's not particularly hard.

The problem with punching through really small metal is that unless you do it cold, the piece cools off really fast. Smallest I did was probably for chainmail, flattened 14-gauge steel baling wire for rings and that was done cold after annealing. Cut snips of the wire for rivets, so say - .08 inches for the hole and rivet? So, the rings are made by wrapping around a mandrel, then cutting and annealing, or the other way around (easier).

When you cut it, you want the ends to overlap a bit, and this makes overlapping flattened pieces on each end of the ring. That's what I punched, but even so, still had some that wanted to tear instead. If I remember right, and it's been at least 10 years, I solved the problem by backing it with a solid piece of soft wood while punching. Made a lot of holes in the wood, but 2x4s are cheap and making chainmail will make you crazy, and I'm already full up on crazy.

did you try drilling it at black heat?  I have had to do it with knives

My grandfather showed me a neat trick to drill hardened steel when you don't have a way to heat it. Take a small piece of rod or a broken drill bit a little bigger than the hole you are drilling. then with the rod like you are drilling it make contact with the steel (I use my drill press) and in short order the steel you want to drill will be at a red heat. Change to the drill bit and drill the hole. That has worked for me many times.

I can’t control the wind. All I can do is adjust my sails. ~Semper Paratus~

Did your Grandfather know my Father Randy or is that a really old trick? I don't remember how old I was when he showed me the trick but it was part of showing me how to drill holes and sharpen drill bits.

I let the normalized stock cool before drilling, so my drill bits last longer. Some steels require time at heat to soften so if it doesn't work let the friction rod work longer or maybe do it a couple few times cooling between.

Frosty The Lucky.

Probably not knowing each other., my grandfather passed away in 1961 or '62 and was a blacksmith in 1914 or so when he was in the army. I think it was an old blacksmith trick.

I can’t control the wind. All I can do is adjust my sails. ~Semper Paratus~

I was being facetious, I HOPE I don't seem that much older than you!

Dad was born on Halloween 1919. Asking him if he was the trick or the treat never got a smile even when he was little, his Mother told me. 

I'm pretty sure spinning an iron or steel rod on hardened steel to spot soften it is as old as steel.

Frosty The Lucky.

this is a tangential question. I have always wondered how the punched the eyes in sewing needles......

As often, "How It's Made" has the answer: