Got a few minutes off work, watching Roy Underhill and a blacksmith-friend turning a 1953 Chevy leaf-spring into a gouge. Them ol’ springs are high-carbon steel, he says. Pretty fun.
Actually very interesting. I think there were 3 different heating and cooling processes after it was cut. I didn’t realize there are several different colors during the last 1 or 2 heatings, and he had to get just the right color (therefore just the right tempering) down toward the cutting end.
Experts! What was that deal where you test it with a magnet, it doesn’t stick, so you go to the next step? Missed that.
forestgirl — you can take the girl out of the forest, but you can’t take the forest out of the girl 😉
Edited 5/27/2006 6:22 pm by forestgirl
Replies
Hmmm. My first car was a '53 Chevy. I suppose if you were compelled to make a gouge out of an automobile part, a leaf spring would be a good choice. Good quality steel used in springs.
Yes heat treating is a an interesting process - almost an art. When you heat steel to a certain temperature it turns cherry red. At that point the molecules have surrendered much of their previous properties (one being magnetic attraction) and you can do pretty much what you want with it. Like pound it into different shapes. Then there is the quenching and reheating to get the steel to the hardness suitable for your application. Of course if you keep heating it, it will turn liquid. Do that in your shop ad things can get ugly :)
It makes me nervous to think of Roy messing around with red hot steel. He didn't end up with any third degree burns did he?
-Chuck
When a magnet does not stick, it has made it to quenching heat, (dark red), for hardening, that can be in water or some type of oil. After that, the tempering process, reheat to a specific temp, maybe 350 to 400 deg, (a straw color). That makes it tough, takes out the brittleness and maintains edge holding.
The other guy with Roy is Don Weber, he teaches blacksmithing, toolmaking and bodgering, (English windsor chair making), in Paintlick KY
Don seems to be a very happy guy, while working with red-hot metal. He obviously knew Roy's propensity for hurting himself as he reminded him not to step on the pieces of metal that fell off onto the floor.
I was intrigued by not only the various colors the metal will turn (peacock blue, bronze and straw are the ones I can remember) but also the different ways they cool the metal, and why they choose each way. Water was not used in his process, only wood ashes and 40-weight motor oil. He gave a cursory explanation of what happens to the molecules. And to think people figured out how to do this probably before they had even identified "molecule."forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
Cooling in wood ashes is the way to anneal/soften the steel so it is easier to shape and grind. Different cooling mediums affect the steel by how fast it cools, oil is slower than water, and solid fats are slower yet. The faster it cools the harder and more brittle it is. I have used a combination of used transmition fluid and used motor oil with grate success. If you do not know the exact type of steel oil is the safe bet.
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Our ancestors were pretty smart, huh?
Edited 5/28/2006 4:17 pm ET by Napie
"Our ancestors were pretty smart, huh?" No kidding. Ingenuity-Plus!forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
Water was not used in his process, only wood ashes and 40-weight motor oil
*************Mike Williamson, a friend who's a bladesmith, uses used crankcase oil for quenching O-1 steel. According to him, it works better (i.e., produces less scale) than water.Table for heat-treating spring steels:http://www.admiralsteel.com/reference/heattrt.htmlStainless steels:http://www.admiralsteel.com/reference/sstltech.htmlLeon
The "O" stands for oil hardening. W-2 would be water hardening and A-2 is air hardening. Most high carbon tool steels can be hardened in oil or water.
When the blacksmith shoes the horses, he uses water, LOL. From what I gathered watching this program, the ashes and oil cool slower and that is a good thing for making a tool. (Overgeneralization? Maybe. One of those episodes I'd love to have on tape, but this new DVD/VCR has surpassed my ability to read directions.)forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
Jamie,
Farriers work is very different from toolmaking, particularly the modern stuff where most of the heat treatment is cosmetic. (for the benefit of the comsumers sense of pride). It is interesting because the metalurgy of modern shoes is almost the opposite of what we are trying to achieve with our tools.
Modern horseshoes are made from maleable mild steel that does not require heat treatment unless you are so incompetent that you work-harden the shoe until it breaks (I've done that). The ones you buy in Australia dont have sufficient carbon to harden anyway. One of our shoe manufacturers commented that at least if his soft shoes wore out there was some chancce that the horse would be shod on time.
The only difference is if you are making special shoes from scratch. Some corrective techniques require making shoes that are unevenly weighted from one side to the other. Iron has to be hot to do this and they are typically quenched so that they can be handled quickly (meaing 8-9 horses a day). Some draft shoes were hardened to handle made roads. I've watched that, and the people doing that also used their fires to get more carbon into the iron. Dont know enough about it to say what was going on.
Metals loose their magnetic attraction when heated. At the temperature that a magnet doesn't stick you quench it to harden it. Then the steel is very hard and unuseably brittle. To soften it you then heat it to a given (lower) temperature and then requench. You can look for a colour change ( straw yellow, blue, cherry red- you can find charts that equate colours to different temperatures and hardness given). The more you heat the metal on the second heat the less hardness it will have and the more flexibility.
If you are going to all that trouble, I'd actually purchase a known steel (like A2) that will have specific hardening requirements. It is far easier to reheat in a toaster oven with a thermostat then by eye.
It is much harder to properly heat treat a tool then to forge it.
Frank
My horse-memories are going back to 1980's -- I had to stop riding at the end of that decade. My best farrier did alot of his own "corrective" work, he's was a good diagnostician in addition to being a great farrier! He also invented, patented and sold to one of the big companies some specialized caulking gun back then. Good ol' Danny.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
That" critical temperature" is when a magnet won't attach.
Work Safe, Count to 10 when your done for the day !!
Bruce S.
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