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User:Stever/Projects/rondeldagger: Difference between revisions
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With most of the parts now made it was time for a test assembly. The first stage of the process was "burn-in" the tang of the blade by heating it up to about 400C and then pushing the handle over it until the heat burns the opening wide enough for the tang to fit snugly. This had to be done before the final hardening of the blade as otherwise the heat from this process would ruin the temper of the blade and make it impossible to sharpen properly.
All the parts now
New tank fabricated it was back to the forge for the blade to be normalized and straightened (and re-normalized, and re-straightened, and re-normalized and..... you get the idea). Once the blade was stable and relieved of all internal stresses it was put through a process of grain refining which changes the structure of the metal to adjust the size of the crystal grains within it. Doing this maximizes the strength and toughness that can be achieved without lowering the final hardness too much. In the final forging process the blade was then heated to 900C, held at that temperature for a couple of minutes, and then plunged into the oil. After hardening the blade was cleaned up and the scale removed using the [[Tools/polishingwheel|buffing wheel]] before hardness testing. Testing it with the [[Tools/hardnesstester|ultrasonic hardness tester]] revealed a final surface hardness of around 53HRC which is a good hardness for this type of blade being hard enough to take a good edge but still tough enough to withstand hard use.
The blade was then re-cleaned and final re-shaping done on the large linisher using specialist ceramic belts before being moved to the [[Tools/smalllinisher|small linisher]] to put the bevels on the cutting edges. With an approximate edge formed it was over the [[Tools/polishingwheel|polishing wheels]] to move through the coarse, medium and fine wheels to put a mirror shine onto the blade, before it was then sharpened with the sharpening stones set. It has to be polished before sharpening as action of the polishing wheels will round-over and ruin a sharp edge. The stainless steel sections were then buffed using the coarse, medium and fine scotchbrite wheels before being polished in the same way as the blade. The use of the scotchbrite wheels turned out to be a mistake as they rounded over the precision-made opening in the guard so the blade no longer fit tightly into it. In the end this wasn't a problem as I was able to position them correctly before gluing but it's definitely something I'll do differently next time.
The parts were all laid out carefully and cleaned with acetone, and then masked off and glued with epoxy resin, this is another thing I'll do differently next time. It turned out that removing the masking tape without marring the surface finish was extremely difficult, so next time I'll try letting the resin set to a more gloopy stage before putting it all together, and cleaning off excess with acetone before it fully sets. A heavy clamp was put on the back of the tang and hammered down to make that everything was snug, then the whole assembly was put into the [[Tools/oven|process oven]] at 40C to cure for 4 hours (probably longer than necessary but I wasn't taking any chances after this much work)
Once cool I used a dremmel tool to reduce the end of the tang to a stub less than 5mm diameter and 100mm long so that it could be fitted into a small peen block to retain it. Over to the metal lathe, I used some scrap stainless steel we had to make a small button-like peen block about 5mm tall and 20mm wide with a beveled edge. Once that was made and cleaned it was time to use the [[Tools/TIG|TIG welder]] to secure it onto the end of the tang. This isn't a common method as it's more usual these days to use an oxy-acetylene torch to heat the end of the tang and hammer it into a taper in the peen block, but the lab doesn't have an acetylene torch for safety reasons and this worked quite well. The end of the pommel was then polished like the rest of the dagger.
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