Saturday, May 7, 2011

My Final Project: Part III

I was unable to take pictures of it, but the next step of the heat-treatment was tempering. Tempering is converting some or all of the rigid, brittle molecular structure of the hardened blade into another that is much more durable and flexible, but retains the hardness. This is achieved by heating the metal up again to another critical temperature, keeping it at that heat for an amount of time, and then cooling it very slowly to room temperature. The file I happened to have is most likely made out of 1075 carbon steel, and its critical temperature is somewhere around 475-500 degrees Fahrenheit. I wrapped it in tinfoil so it would heat evenly and stuck it in my dorm lounge oven for about an hour when the oven reached that heat. Then I turned the oven off and allowed it to cool completely. When I took the blade out, I could bend it both ways up to maybe 25 degrees and returned absolutely true. It was now a true blade.

The next step was making a tool with which to scrape the decorative grooves I wanted based on historical examples. I learned about this tool on Don Fogg's very helpful bladesmithing site, and I made my own version by drilling and tapping a hole to screw in a carbide lathe bit, welding on a stabilizer, and drilling holes for an adjustable fence, which I had to screw on using a square to make sure it was, you know, square.

Then I custom-cut a piece of wood to clamp the blade on, with one edge in the exact shape of the groove I wanted to score. I calculated the placement of the blade and began scraping!

It worked surprisingly fast! I had four grooves to carve, two on each side meeting on a point, and I did the whole thing in less than an hour.

On the last groove it was getting late and I was tired, but I wanted to finish this step. I paid for my impatience by slipping with the tool and scraping parts of the blade I didn't want to, resulting in scratches that are still there. But overall it worked quite well, and I won't do that next time!

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