Spence-
Yeah, the point on Bura's version was at _least_ as thin as it was on the model, and absolutely dead soft. It had some penetration success against live trees, but it bent when smashed into old firewood. (I wonder if Sanu's version is different. I hope he made the handles match on his.)
In any case, the point was just way too thin, especially in the distal taper, so I ground the needle-like first 1/4" off and reshaped from there. The tip is now a lot stronger, and fine against firewood, but the crazy thing was that after I knocked off the initial fragile tip, the steel beneath seemed much harder.
This is something that I've never run into with a khukuri before. My experience with khukuris has always been that if the tip is real soft, you can hammer it and grind it but the newly exposed steel will be just as soft. That does not seem to have been the case with this katar blade. I have a couple of possible ideas as to how this might have happened but the only way to know for sure would be to watch how the kamis hardened these things in the first place.
So, after having good success regrinding the tip, the whole thing was welded, and straightened
, and more or less cryoed.
Rust asked about cryoing-
I went to the Phoenix public library and checked out "Cryogenics" by William E. Bryson. The book claims that many materials, and especially ferrous materials like blade steels and tool steels, can benefit greatly from exposure to extremely cold temperatures. The theory is that after forging, quenching, and tempering, the molecules in, say, a knife blade are still somewhat jumbled up and some internal stresses remain regardless of how well the heat treating process was done. As the steel is cooled down through exposure to dry ice or liquid nitrogen, the molecules slow down and eventually realign themselves more evenly than would be possible through conventional heat treating alone. As a result, internal stresses (say, from welding or heat treating) are reduced, and wear resistance (useful in everything from khukuris to drill bits) is greatly increased through transforming more of the retained austenite, or something like that. That's the hope, anyway.
What I did was unfortunately far from perfect. No one in Phoenix seems to offer cryo treating anymore, so I went to a welding supply house and had them fill up a couple little 5 litre dewars that I rented from them. I then took them back to the shop where I had stood up a rubbermaid bread loaf holder inside of a large styrofoam cooler lid. (The dewars weren't big enough and the rubbermaid bread box was the longest container I could find that was still broad enough to put the katar in, while the styrofoam lid was for safety in case the liquid nitrogen shattered the rubbermaid thing.) I started pouring the liquid nitro into the rubbermaid container and while there was plenty of hissing and boiling, there were no leaks and nothing shattered. I filled it most of the way up and then went to the freezer to fish out my pre-chilled katar. Into the liquid nitro it went and I was in business.
The rest of the afternoon was spent occassionally topping off the container as the liquid nitro boiled off, and then eventually wandering off to do something else when I ran out of more to pour in. Total time in cryo at the tip may have been up to four hours, which has to be better than just putting it in the freezer but certainly isn't as good as a professional facility could do.
After the blade warmed up to room temperature, I put it back in the oven for one last tempering cycle to relieve any stress caused by the liquid nitro.
Unfortunately, I wasn't yet nearly done with the damn thing but I think I'm tired of telling stories for the time being.
I'm getting pretty sick of working on the damn thing, but I still need to test it out against some sort of serious opposition like a car door or something like that.
Hopefully this weekend I will be able to get to my grinding wheel to begin work on a new and improved 15" version of this katar with a forge-welded frame.
Anyone who wants to order one of these things from Uncle Bill might want to see what Big Bob has to say about his. These first two may be more like initial prototypes--as yet there remains much room for improvement in my design.
-Dave
Seriously, please let me know if you have any questions/comments/criticisms about it; any shortcomings in design are entirely my fault. And let me know if you plan to make any modifications so you can avoid repeating the mistakes I made.
