Forging and Metallurgy 101

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So far I've only spent two days at the forge, since my mentor Arnon was sick on Monday, but both days have been awesome. I also have today off while Arnon works from home on parts of the business that don't require the shop, so I'll try to write a lot. I'll also put in some links to pictures I find online of tools that are difficult to describe in text so you can get an idea of what I'm talking about without me wasting space trying to explain them.

Before this project started I was wondering how Arnon would be splitting his time between teaching me and doing actual work, and so far we've found lots of ways to do both things at once. On Tuesday, we spent half the day working on some steel parts for tables. The customer, from what I gathered, is a hotel that has a bunch of tables with detachable leaves. The problem they encountered is that people tend to sit and lean on tables, and enough people putting their weight on the table leaves caused the parts holding them up to bend. Arnon's job was to make parts to fit the tables that won't bend when inconsiderate people sit on them. He made all of the parts out of mild steel, which is a relatively low carbon steel. It's normally really easy to bend, as he showed me, but if you know what you're doing you can heat treat it to be much stronger. This is done by heating the steel up to its critical temperature (the temperature where the structure of the metal changes), and then rapidly cooling it so that the metal doesn't have time to revert to its original structure. This is a fairly simple explanation since I haven't really had time to learn about the actual chemistry of what's going on, but it's sufficient for understanding the effect. Water, brine, and oil are some of the more common quenches (liquids that the metal is plunged in to cool), but we needed something that would cool the metal even faster, so we used a solution invented by a famous blacksmith called "super quench".

To make "super quench", you saturate water with salt, and then add Simple Green and Dawn dish soap (or any similar cleaning products). Why does this make it quench faster? Normally when hot steel is plunged into water, a layer of steam forms around the steel that pushes the water away, and that makes the steel cool much slower. The soap in the super quench makes it harder for the steam jacket to form around the steel, and keeps the steel more in contact with the water. To make it cool even faster, you can vigorously stir the steel back and forth to break the layer of steam. There's a fairly interesting story about the guy that invented super quench, and you can read about it here.

We had 36 parts that needed to be heat treated, and I was responsible for quenching most of them while Arnon did other things around the shop. After about ten parts, the water had warmed up so much that Arnon decided we should go out to the store and buy chemicals to make more, as well as some ice to cool the original batch. At the hardware store I found the Simple Green (thanks to my familiarity with the bottle after filling mop buckets in the theater), Arnon found the dish soap, and we left with everything we needed. After quenching all 36 parts, both batches had gotten hot, and we probably wouldn't have been able to quench any more without waiting. After that I got to sand blast the parts using a big sandblasting enclosure, which was pretty cool (it had two big rubber gloves to stick your arms in, and looked like this).

When I haven't been helping with jobs, my time has been spent learning the basics of forging steel from Arnon. On Tuesday he taught me the basics of holding and using the hammer, and I practiced turning my left wrist (the one that holds what you're working on) to make 90 degree angles and square up a round bar. The next day I learned how to take a square end of a bar, turn it into a square point, and then round that point out into a smooth, conical tip. After I had gotten that down, he also introduced the leaf shape, which is created by squashing the center of a rounded point into a flat, curved shape. This leaves a neat little point on the top that makes it look like a small leaf. If you've ever seen a big wrought iron gate, this is one of the common shapes to put on top of the vertical rods because it's pointy enough to deter trespassers while also adding to the gate's appearance. I tried making a couple leaves, and they were a little bit lopsided. Arnon is incredibly skilled at making them; his master in Israel had him make ten of them every day before he started his work, and he was only allowed to heat the steel one time for each (it took me about six heatings just to make the rounded point).

In the two days I've been at the forge I've had lots of little interesting conversations with Arnon, and he says lots of insightful things. When he was having me practice my accuracy with a hammer, he asked me: "Why is it that nobody can just hit the same place every time? Why can't anyone just play darts and hit the bullseye with every dart?" I said I didn't know, and his response was "Nobody does, that's just how it works". At some point he also told me that master smiths aren't incredibly accurate with every hammer blow, they're just really good at watching for what they screw up with each blow, and fixing it with the next one. I also overheard an interesting conversation between Arnon and another guy from the business complex. The other guy was talking about how it was sad that smithing was dying out as a craft, but Arnon asserted that it has actually been growing. There are lots of things that are way easier to accomplish by forging, especially jobs like the table parts that are repetitive, but not enough hassle to need a factory. It's also really hard to get shapes that blend together (like the leaf) with machining or casting. Smithing is really adaptive, and there is a lot of mixing of old and new technology. For insatnce, yesterday Arnon had a jig that needed to be put into his power hammer, but there weren't handles for him to pick it up with. To fix that, he had me help him score and bend two flat bars (using a forge, a sledgehammer, and a fuller) into some makeshift handles to attach to the sides. Arnon loves using more modern technology like power hammers when they make things easier, but he also won't hesitate to go back to the basics for things that don't need big machinery. That's one thing about the media that annoys him--when they show a blacksmith, they want to show a guy smacking a piece of hot steel and sending sparks everywhere because it's romantic. They don't think people want to see a guy using a big power hammer to get the job done faster, even if that's what a lot of the work entails.

So far I'm really enjoying this project, and I think it's only going to get better as we move into more advanced topics. Arnon seems really enthusiastic about helping me make a knife, and whenever it's relevant he'll relate some of the basic things we do to knife making (heat treating, for example). I'll try to take more pictures, and get some videos of forging, because it's hard to capture in pictures.

Attached to this post are some pictures of the pointed tips I made (in order of my progress), some normal leaf shapes, and one large leaf that was made by first scoring some circles into the rod, and then flattening it. There are also a few pictures of my workstations from the past two days. The pictures are all resized by the uploader, so I'll probably make an album online with all of my pictures from the whole project in full resolution (or at least, bigger than 1024x768).

Comments

Thanks Alan

Sounds like a fascinating project. I imagine your days go something like this:
http://www.youtube.com/watch?v=JwP5dkfGmlI

Thank you for the detailed post!

I am curious about the different types of steel you use and why you would use one over another in a particular application. For example, why not just use a stronger steel for the table parts instead of doing the quenching thing? (Materials science is a fascinating field...how the differing chemical components of the material affect its overall physical properties.)

I enjoyed reading the link about the quencher and understand now the need for the different components. (I didn't know that salt raises the specific heat of water...I'll have to use that next year with the freshmen.) What is the "Rockwell" scale?

I look forward to your next post!

Steels and Hardness

The main reason for using mild steel for the table parts was the price. He said that it would have cost him a few hundred dollars to buy enough really strong steel, while correctly heat treated mild steel would be plenty strong for bearing the weight of a person, and all the steel was under a hundred dollars.

I don't know a whole lot about the Rockwell hardness scale, but he has a machine for testing it and he explained the basics of it. The machine has a diamond tip, and some weights. It first tests how far a known weight will push the diamond tip into the material, and then tests how far it penetrates with a heavier weight. The Rockwell number for that material is then somehow determined based on the difference between the first and second distances. When we tested the hardness of the table parts, we didn't need anywhere near that level of precision, so we just tested a few (to make sure the quench was working) by running a metal file along the surface. The metal file is hard enough to file away untreated mild steel, but after it's been quenched the file just squeaks over it loudly and doesn't remove much (if any) material.

Nice post

Cool post and project, I quite enjoyed it. Does your mentor work exclusively with steel? What other projects does he do?

Metals

I think it's mostly steel. One of his main crafts is knife making, which is all steel. I think the rest of his work is little odd-jobs that require making parts for things, and in most cases those are probably steel (for strength and price reasons). I'm sure he has plenty of experience working with other metals, since he was an apprentice to multiple blacksmiths in different countries, but I think the bulk of what he does now is with steel.

"Steel" is still a fairly broad category though--he uses everything from lower carbon steels (like the mild steel I've been working with) to high carbon steels, and stainless steels (steel alloys that contain ~10% or more chromium). They're all steel, but they behave pretty differently and have different applications, so there's still quite a bit of variety.

Wow!

I agree with Nichole - what a great blog post! And I am so glad the project is going well! I feel like I should know more chemistry to understand some of the quenching stuff, so I will ask Becky to read and explain this to me.
Can't wait to visit!

Awesome!!

What a wonderful post, and what a wonderful project! You. Are. So. Cool. Love the pics and the hyperlinks!

Looking forward to reading more. Be careful with those blades!

Nichole

P.S. Hi, Nathan Norris!

Excellent

So that's what a fuller is. Also what a great way to do sand blasting, sounds much cleaner. Looks like your'e jumping right in, which is awesome. Powerhammers are a gift to blacksmiths, and a curse to strikers. Have you ever started the forge or built the fire? I'd be curious to hear how exactly he goes about heating things. Keep making/photographing/posting leaves, that's the kind of thing that makes a blog and a presentation really fascinating.
Keep it up!

Heating

He has a few forges, and they all run on gas. He might have something for using coal but I haven't seen it, and if he has a coal forge he probably never uses it, because gas is way cheaper and has less environmental impact. The forge I used on Tuesday was hooked to a natural gas line, and it had an air compressor to increase the pressure (the gas only comes in at like 3 psi). Yesterday he needed the small gas forge, so he set up a portable propane forge for me. It looked sorta sketchy but it worked great, and it's actually better at heating things evenly due to its shape. There are pictures of both of the forges attached to the post, but I'll try to get some better pictures of the stationary one.

I didn't get to start either of the forges, but it seems simple enough. You turn on the air, turn on the gas, and light it with a lighter. Or alternatively, for the bigger forge I saw him using, you can take a rag soaked with flammable liquid, set it on fire, put it in the forge with some tongs, and then start the gas. The harder part, from what I've observed, is getting the balance of fuel and air flow correct. You want a nice steady stream from the burner, but you don't want excess flames belching out the front. I think I could do it with some fiddling, but he's had enough experience to where he can tell what to change just by listening to the sound.