BlissStreet Posted September 21, 2011 Author Share Posted September 21, 2011 Use a temper color chart. I use the home gas oven. I set the temps close to where I know it was the last time I did that steel, BUT I have the blade polished and shiny so I can read the color of the oxides to verify what temp it was really at. The Oxides do not lie, but we can misread them a bit. Check. A convection oven uses a fan to circulate the heated air. This changes the heat transfer rate, increasing it greatly. This increase in rate is why when cooking you need to reduce the temperature so the heat can penetrate the food without burning. With a knife that you are tempering it should eliminate hot and cold spots creating a more even result (remember to accommodate for radiant heat effects from the elements if necessary) but the final temperature is still the same, so the oven setting would be the same. Roger. Feeling mono-syllabic tonight, lol. Quote Link to comment Share on other sites More sharing options...
BlissStreet Posted September 23, 2011 Author Share Posted September 23, 2011 Hey guys, I have some news. After giving your feedback some thought, and getting really XXXXXX at the XXXX BMW coil spring, I did some calling around. So it turns out that Toyota uses leaf springs in a variety of vehicles. And they are consistent in their standards for the steel used. (turns out there is a Toyota employee that makes knives and has done all the leg work for me). They use a standard of steel called JIS SUP9A, which according to this pdf file is same as SAE 5160. I bought a leaf spring, which is a lot of steel. But...a known steel. This should take some of the guess work out of the equation. Right? guys? Quote Link to comment Share on other sites More sharing options...
pkrankow Posted September 23, 2011 Share Posted September 23, 2011 Did buying a leaf spring cost less than buying steel? Did you get a good used or a broken used or new? If the spring is not know to be a part produced by and for Toyota, but instead an after market part from someone else bets on it being truly "known" are off, however whatever the source the likelihood of being 5160 is good. Test samples before trying to make something top notch (and potentially being wrong days of labor in a project). It is mentioned in other threads, but custom suspension shops exist in all major population areas in the driving world, have you contacted them about getting some short drops? 2-4 inches of spring stock can become many things, especially if it is of decent diameter. Phil Quote Link to comment Share on other sites More sharing options...
thingmaker3 Posted September 24, 2011 Share Posted September 24, 2011 Did buying a leaf spring cost less than buying steel? Phil has a good point. I can get 5160 drops from a local spring shop for $0.75 per pound. That's only a quarter more per pound than my local junk yard charges for mystery steel. Quote Link to comment Share on other sites More sharing options...
cracker72 Posted October 2, 2011 Share Posted October 2, 2011 Hey Bliss, I had the same thing happen to me for the first time a few months ago. I work with "mystery" spring all the time but this one piece would just split and crack as I was drawing it out. I threw it out the door and grabbed another - no problem. That's as far as the investigation went. Quote Link to comment Share on other sites More sharing options...
Randy Posted October 4, 2011 Share Posted October 4, 2011 I've been using car/truck/garage door/etc. coil springs for some time with good success. In teaching that is all that I use and the students have no problems either if they follow the lesson. As stated above, don't over heat or hammer too cold. When starting with a new spring (new to you) heat it up on top of the fire slowly in the area that you want to cut. Then place it in the fire and again slowly heat until bright orange and then cut off the length of piece that you need, usually over the horn using a slit chisel. Don't cool off the remainder of spring in water, but put it on a brick or somewhere to slowly cool off. I should mention that if the spring material is under 3/8" round stock or under then you can heat up a large section and slide it over a bar in the vise and pull a section straight and then cut to length. Pull it perpendicular from the bar in the vise not the other way. Take the cut off piece and slowly bring up to a medium to high orange heat and straighten out. Keep inspecting the piece for cracks. If you have any cracks then pitch the whole spring. This is very rare, but it does happen even with proper proceedures. It's not worth the risk. (I also cut a sample piece, about 2" to 3" long that I bring to a chisel end and use for a sample piece to test hardening mediums.) Try another spring the same way. When done forging slowly heat to a medium cherry and then place on a fire brick to slowly cool (normalizing). Once cool check for cracks again. Now you're ready to harden and temper. Try the sample piece first. Heat slowly until it loses its' magnetism and then quench in water moving the piece in a figure 8 until cold. Check again for cracks. If there are no cracks then you can use water for your quenching medium on every thing you make from that spring. Now you can heat the chisel/ punch end about 2" slowly and thoroughly. This is the working end only. The hitting end should just be normalized, never hardened. Do the same process for hardening and then temper the tool for whatever use it will serve. If this particular spring needs to be quenched in oil or if when done is particularly tough, I mark that on the remaining spring. Actually I have never used anything but water for quenching coil springs, but each new spring I check first to make sure that I don't have a particulary brittle spring. Quote Link to comment Share on other sites More sharing options...
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