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| S. Heslop:
--- Quote from: awemawson on June 12, 2015, 09:31:52 AM ---6" clay or iron drainage pipe would work, but why can you not just let them cool in your forge - I doubt it'll cool fast enough not to leave them soft ? --- End quote --- Yeah it surprised me when it didn't work because that's what I tried the second (I think?) time. Also I think the problem with moisture isn't things getting literally wet, but them absorbing water vapour. The vermiculite was dry to the touch but still gave out a surprising amount of steam. Also also I took one of the files out the bin and touched the tip of it into some water, and it seems to still be above at least 100°C after an hour. So it's at least cooling faster than in air. |
| vtsteam:
--- Quote ---For most tool and high speed steels, the annealing temperature is about 1600 degrees F (870 C). The tool will need to be held at that temperature for hours. A good rule of thumb is one hour per inch of thickness with a minimum of 2 hours. The second stage of the annealing process is a slow cooling process. After the tool has been heated and held at the proper temperature, it needs to be cooled at a very slow rate. Generally this rate is 50-100 degrees F (28-56 C) per hour. This is usually performed by leaving the tool in the furnace, turning off the heat and keeping the door closed. The tool can be cooled in still air after the temperature of the tool falls below 1000 degrees F (540 C). After the tool has reached room temperature, it is soft and able to be machined. --- End quote --- I imagine they're talking about a considerably larger furnace and a sealed one at that, to get that slow a cooling rate. For me it was easy to just put the part in the wood stove embers and leave it -- I don't think I had it in a full hour, but it wasn't just heating for a few minutes with a torch either. Then bury it in a bucket of wood ashes, which I'm sure cooled very slowly, and were dry. One nice thing about a solid fuel fire is it will die out slowly, so that's another possibility -- put it in coals, or wood embers, keep it hot for awhile, and then let the fire die out naturally around it,. It will likely be covered in ash as well. Seems like a natural for the barbecue, if you have one. |
| vtsteam:
A lot of good info on annealing high carbon and alloy tool steels here: http://www.anvilfire.com/article.php?bodyName=/FAQs/heattreating.htm looks like it might have to be VERY slow cooling, depending on what alloy you happen to have. The one surprising point in your case Simon is that you seemed to succeed in making the blank soft the first time since you were making rasp marks in it easily. So the question is why, and what changed? Diffrent blank? |
| S. Heslop:
Yeah the vermiculite didn't work. We do have a barbecue but it's fairly shallow. But I did notice that my grandad has acquired a real giant charcoal bbq, the half a drum type. I also noticed that the files just barely fit into the metal melting furnace, with the tips of the tangs poking out through the hole in the top. Perhaps I could do something with that. I think I remember reading that a tangential inlet doesn't work so great with charcoal but perhaps a strategically placed bit of firebrick might help direct the blast. |
| S. Heslop:
--- Quote from: vtsteam on June 12, 2015, 11:55:35 AM ---A lot of good info on annealing high carbon and alloy tool steels here: http://www.anvilfire.com/article.php?bodyName=/FAQs/heattreating.htm looks like it might have to be VERY slow cooling, depending on what alloy you happen to have. The one surprising point in your case Simon is that you seemed to succeed in making the blank soft the first time since you were making rasp marks in it easily. So the question is why, and what changed? Diffrent blank? --- End quote --- The first time I heated it up red, then stuck it into the embers of a dying wood fire. Half the file was still poking out though since the fire wasn't big enough. Plus I was using high speed steel to punch those marks, so that might've helped. The stuff i've been trying to make punches from does harden, but it can still be (just barely) filed. So it's not as hard as it should be. I also tried grinding a bit into that steel to make sure I wasn't just filing off a decarburized layer. Hopefully Andrew's bits of rebar will work better when they arrive. Y'know it'd probably be diligent to try the high speed steel again. I had the tip snap off (which is to be expected) trying to punch it after the first hardening-steel chisel didn't work, and I never tried it again. |
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