Making a Knife, Part II

Dec 20 2014

Made some good progress over the last few days. First I did a lot more filing and got the shape of the knife pretty well fleshed out.

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Next, I filed down most of the bevel of the blade and drilled a couple of holes in the handle. Dowels will hold things together. I also sanded the whole knife and then polished the blade with abrasive paper up to 1500 grit. In retrospect, this was a waste of time since I’ll have to do it all over again after the heat treatment, which leaves lots of oxidation all over the blade which needs to be sanded off.

Note that there is not really an edge on this yet. I filed the bevel down to leave about a millimeter of width on the knife edge. This is because you don’t want to have a super thin edge during heat treatment, as this will heat up too quickly and start to oxidize. After the rest of the knife is done, I’ll put the final edge on it.

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Next came some brass pieces for bolsters. I drilled a couple of smaller holes in the knife and cut off two pieces of 1/8″ brass. Lining those up with the blade, drilled matching holes in those and held everything in place with some 16 gauge brass wire.

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Next came shaping the brass, first, filing it in place on the knife so it is even with the top and bottom edges.

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I then took the brass off and filed the front and back edges even with each other.

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And finally the heat treatment. First, I used a MAPP torch to heat the whole blade to a cherry red, then quenched it in oil to fully harden it. I see now that I’m at about the limit in terms of size that I can do with a plain torch. It was really hard to get the entire blade to stay red. If I moved the flame towards the back, the tip would cool down. When I went back to the tip, the back part would go black.

I wasn’t happy with the first attempt. So I used a few bricks to create a makeshift torch kiln to concentrate the heat. This was barely adequate. I think I got it solidly red long enough before quenching. I don’t have any photos of this part because 1. I was holding a torch, and 2. I needed to move fast. I need a photographer.

After hardening, I needed to temper the blade, otherwise it would be too hard and brittle. This involves bringing it up to a lower heat and letting it cool again. This is best done by color. You look for a “straw” color, particularly along the edge of the blade. You can go up to blue or purple on the back. Earlier, I’d done this in toaster oven, but since then I’ve read that you can just do it with a torch. I like this method much better. So much quicker. First I had to sand all the carbon off the blade from the hardening, to get it nice and shiny. Then I set the torch to a lower flame and played it over the back of the blade. Before long, the whole thing was straw colored and then the purple and blue showed up, right on schedule. Pretty impressed by how this part went.

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And that’s where I’m at. I re-sanded and polished the blade. So it looks just like it did in the earlier photos.

From here, I need to attach the brass, cut some wood for the handle, drill that and attach that. Then shape, sand and polish the handle and bolsters. Then I’ll be ready to put a final edge on the blade and hone it.

All this sounds like it’s a lot of work, but honestly I’ve spent a surprisingly few number of hours on this so far. And if I pick up a belt grinder, that will cut huge amounts of time out of the process, compared to hand filing.

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