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A very interesting video!
vtsteam:
--- Quote from: mattinker on July 11, 2017, 12:58:59 AM ---All of the Clickspring videos are interesting! I thought of you Steve (VTsteam) when I saw this!
--- End quote ---
Absolutely fascinating! Loved it Matt. Thank you! :clap: :beer:
vtsteam:
It's funny because I had found myself thinking about case hardening again, last week after re-reading the attempt at a mod-up I did a couple years ago. So I watched the Clickspring video tonight about that case hardening, too. Lots of new and useful information, and he does a really superb job of neatly working on camera, and filming and editing. First class job!
I do find I have some questions about the method for making the files, and perhaps I will try it myself when I can, just to find out the difference.
His method is to cut the files first then case harden them, and finally temper.
I was thinking of case hardening and then annealing, then cutting teeth and hardening followed by tempering.
The tricky point is the heat and exposure to oxygen after cutting the teeth in either procedure. Because that degrades the tooth sharpness. His method would at first seem better that way, as the hardening stage is in an oxygen poor casing of his pack mix. But I noticed he cracks it off in the presence of air. I saw a fair amount of scale (oxidation) as the pack was removed, and during the slow plunge. It also seemed to take a long time to plunge.
I was wondering if the heating to harden in my second proposed method could be done in a slightly reducing atmosphere, and then a quick plunge into water, reducing oxidation and better preserving the teeth? I don't know how well the tooth making would go in annealed case, either. But something to try some day.
I guess the proof is in the pudding. Wish I didn't have so much I have to do at present -- including finishing the lathe.
S. Heslop:
That method for case hardening looks useful. I tried a while back to case harden in a sealed steel box filled with charcoal powder, and it burst open and flung the contents out. They were thankfully only a little warm but it was enough to make me nervous about trying it again. I figure the clay is permiable enough to prevent that from happening, but it'd still be a little scary.
--- Quote from: vtsteam on July 11, 2017, 10:41:58 PM ---I was thinking of case hardening and then annealing, then cutting teeth and hardening followed by tempering.
The tricky point is the heat and exposure to oxygen after cutting the teeth in either procedure. Because that degrades the tooth sharpness. His method would at first seem better that way, as the hardening stage is in an oxygen poor casing of his pack mix. But I noticed he cracks it off in the presence of air. I saw a fair amount of scale (oxidation) as the pack was removed, and during the slow plunge. It also seemed to take a long time to plunge.
--- End quote ---
I saw that commercially they heat files for hardening in a molten salt bath to reduce oxidation. Seems like an awfully dangerous thing to mess about with though. Also even then the teeth dont come out perfect, so they give them a quick sand blast to clean the teeth up and sharpen them. An acid bath might work too, I think i've heard of that being used to sharpen worn files.
When I made those rasps I was using as reducing an environment as possible, and also rubbing the the thing with regular bar soap. The soap didn't really stick to the rasp once it got hot, but it seemed that it did help. They came out not too far from how his files did after case hardening though, along with some light cracking.
mattinker:
--- Quote from: S. Heslop on July 13, 2017, 07:13:20 AM ---
I saw that commercially they heat files for hardening in a molten salt bath to reduce oxidation. Seems like an awfully dangerous thing to mess about with though. Also even then the teeth dont come out perfect, so they give them a quick sand blast to clean the teeth up and sharpen them. An acid bath might work too, I think i've heard of that being used to sharpen worn files.
--- End quote ---
Letting files rust is a way of sharpening them, it works well!
seadog:
In the same way that reapers used to leave their scythes out to weather. A quick wipe with the whet stone come harvest time and they were razor sharp.
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