30cal_Fun

Hi Matt, (1) I have that one saved, it was a good read but this is also one of the articles that got me confused in the first place. (2) Nope, not counterintuitive at all. I do know a lot about these kind of things, and your right. The purpose of the thin clay layer is twofold: it makes a bigger surface for the water to contact so that the heat transfer of the steel to the water is quicker, thus improving hardening. And the clay makes for a less abrupt change from water to steel, so that the steel does not contact the water directly. The results: less chance of cracking, more controllable and improved hardening. The coil springs are from a car, does that mean they're 5160? as far as I know car coil springs are usually 1095. Louis

Frank and Matt, I appreciate you both taking the time to answer my questions. I know there is a lot of knowledge around and is just waiting to be read, but I just wanted a starter on oil quenching. I have read a lot of posts here and on other forums about water and oil quenching, but I have always used water so far, and I know the Japanese have done so and are still doing so with great success, so all the things I read where confusing me as to which extent water could, and oil should, be used for hardening. In the two posts above there is for now all the information I wanted of the whole oil vs. water thing. And like you both explained; the rest is up to me to fill in all the background info. Thanks for all the tips and info, I have a good picture now about how to go at oil quenching. I have found some coil springs, which should be 1095 of the likes, and with some luck I will have a lot of leaf springs too in a week or so. The coming time I am just going to experiment a whole lot with quenching these steel and work from there. Louis

Hi Dan, That's a petty, but I can understand it, I was thinking exactly like that when I was just starting. "forge, ah well, it's just a hole in the ground with two mounds on the side and air blasted trough it, what can be so difficult?" But the four points you mention make a big difference. I have a friend that studies architectural engineering (if that's the proper English word), I was hoping that I could borrow some knowledge from him, but they are just starting in airflows and things like that. An inch more or less can make a big difference for how the forge performs. I have been trying to get some information about airflows, heat dispensation, conduction etc. but It's a very hard nut to crack. About the charcoal, the process is called Sumi-wari in Japanese and like you said it is a very important step in the forging and hardening process. This link I have saved gave me some good info about that: Sword making process I am starting to have doubts about my new design, I am worried that I might get a small fireball on the base of the forge and that it doesn't have enough room to spread it's heat upwards without risking over-heating (and burning away) the charcoal on the bottom. I made some changes that would get me closer to the original Japanese style design that I had put aside. This would make a good fireball on the bottom of the forge with plenty of room for the heat to dispensate. I have included the picture. The squares are like the first drawings: one square is (in real life) 2x2 inches, so the scale is 1:10. The pencil stripes in the second drawing is how I expect the air to flow. Let me know what you think. I have a lot of respect for you building your own house, I don't know anyone that would go at it like that. Good luck with your new house and forge!! let us know how it's coming along. Louis

Hi Danocon, good to have you on the forum. I have seen your website with the forge long ago, it was very interesting and educational to see how you went through the whole process of building your forge. When I look at your design, the pipe is about 2inches above the base of the forge and tilted down. Thinking of my old forge, I believe this would get me the exact same problem I had in the first place: that the fireball would be on the bottom of the forge. All the air would be blown towards the bottom and with it all the heat. I want the air and heat to be blown up trough the piled up charcoal and against my blade. With solid fuel forges you don't stick your blade on the bottom of your forge, you lay in on top, with a little charcoal to cover it. Then the air will be pumped in from the bottom, traveling upwards trough the charcoal blowing the heat up against the blade. I am trying to make my design as efficient as possible and be able to get it to hardening and forge-welding temperatures. Seeing your pictures it looks like you put the steel almost on the bottom, right in front the airpipe. I did this too with my old design, but it would not give me enough heat. Does the heat travel upwards or do you put the steel right in front of the tuyère? You said you wanted to change your forge in the future; What would you change about the design then? And why is the charcoal powder bed so essential? Louis

Sounds great! I learned a lot from reading other threads as well. But I was wondering: Will using oil for differential hardening make the Hamon less visible?, will it look differently? or will it be just as bright? Louis

For the past years I have mainly been shaping by stock removal. I have been using simple steel that you can get everywhere here in DIY stores, it has a black coating on it and comes in 2 meter strips of various shapes and sizes. I have absolutely no idea what steel this is, but from spark tests I think it is a low to medium carbon steel, I differentially harden it and it gets hard enough for files to have trouble with the hardened part, my guess would be around 0,30%-0,40% carbon content. This might seems very low for blade making, but it is the experience that counts for me, and I have been able to get some reasonable Hamons out of it. Since I want to get more serious I have been trying to get better steel. I can get O-2 steel here, but getting old car springs (I think they're 1095 for coils and 5160 for leaf) would be much cheaper, so I will try these first For blade coating I have been using 2/3part fireclay and 1/3part powdered charcoal. I then mix it with water till I get the viscosity to my liking. However, I am planning to experiment using refractory mortar, since I hear a lot of people using this with great success. As for the oil; Can I just use cooking oil like sunflower- or other vegetable oil? Thanks for all the replies, Louis

Thanks for your input, any experience is welcome to me. I like old stories like this, they have a pinch of humor in them, but always some valuable lessen too. Japanese smiths always quench in water, even master smiths use regular tap water of ambient temperature. And with great success for over 1200 years. However, I can see your point, steels of the 10xx series are well suited for water quenching. If the blade edge is left about 2mm thick before quenching, the blade won't crack that easily. 1070/1075 steel is probable the simplest and closest equivalent we have to the Tamahagane Japanese smiths use. 5160, because it is a spring steel has very different properties because of it's chemical composition. If I am not mistaking, throwing of scale isn't what I want because the blade is coated with a layer of clay. Since I am going for a Hamon, wouldn't it be best in my case to go for a fast hardening quenchent? I am not familiar with brine, so I will stick with plain water first and see what happens. If all my blades crack, I can still turn to oil. What would be a good (and easy to get) oil to use for quenching? one last question: what do you mean with "Some tools are agitated under the liquid"? I do not understand exactly what you mean with agitated. Louis

Interesting that you mention "The Craft of the Japanese Sword" I have it and it has been a very good read. would you be able to post the pictures of the saw maker you have? I have a map with photo's of Japanese hearths saved to study, my design is very much inspired on these kind of forges and I am always looking for more to learn from. Thanks, Louis

Hi everyone, I have been busy for a while designing a new forge to smith blades in and most importantly: harden them. The old one doesn't work well and stands in the way. This one has served me for many years, I poured it from fireproof concrete, it is reinforced and I made it when I was about 16 years old. It was about four years back and I made it with the little knowledge I had at the time, but was determined to build a Japanese style forge. It gave me a lot of understanding and experience, so it's time for improvement. Foto's of everything can be found here: Foto's of my whole project Now that there is room in my backyard, a very nice 2x2meter concrete plateau, I want to build a new and better forge there. Since the old one is still good, I will use it as a base. With firebrick and cement I will build up the old one to the design I made. On top of the forge I will build a cover to prevent hot sparks and smoke to get everywhere, my neighbours are good friends, so I don't want to smoke em out, and I don't want the trees and hedge to catch fire either. When the forge is full of hot charcoal, and I blow a lot of air through it, it only gets hot on the bottom near the tuyère (airpipe). It won't get me enough heat efficiently on top of the fire to effectively heat blades. My idea behind the new design is that the tuyère blows air in from the side in the bottom of the forge. Because of the upside-down-roof-shape of the centre of the forge, all the air and heat from the charcoal will be pushed upwards. This was the mayor design flaw in the old forge. Because of the flat bottom with the tuyère on bottom level all the air, and with it the heat, could escape on all the sides. No matter how much air was blown in, it was simply blown away to the back and front and couldn't send all the heat upwards towards the blade that is in the fire. Let me know what you think, Louis

Hi, I have been making blades for some years and I try to get as close to the Japanese way of making knives and swords as possible. I differentially harden my blades to get a Hamon, and so far have always used water. However, I read a lot about people quenching in other liquids like oil and even brine. I know that some steels quench-harden better in oil, but I never really understood why. Does it have to do with heat distribution when the hot blade meets the liquid, the chemical composition of the liquid, the viscosity, or even how fast the temperature of the liquid itself rises??? So; which factors make up the choice for the appropriate liquid? will water-quenching give a better Hamon on steels like 1075 or 5160? Let me know what you think, Louis