Friday, January 4, 2013

Bar stock to blades part 2

Getting the rough shape finished is the easy part, it just takes time and wee bit of skill. But changing the rough bar stock to a blade is where the real patience and skill come into play. Again, I'm not a smith, just a patient hobbyist. I make most of my knives with a nearly flat grind that is slightly convex, sometimes referred to as a sabre grind that requires a slack belt to grind on. I add a secondary bevel at the last stage to ensure a shaving sharp edge that can be reproduced and touched up in the field.

During my last goat hunt, when my trophy had to be skinned and quartered on a 35 degree scree chute between ice and a cliff. To touch up my blade I just grabbed a rock by my feet that had a good course grit and touched up my edge so I could keep working safely. This is what a good field knife should be capable of. So that is the goal, how do we get there?

First I flatten the bar stock to a universal thickness, removing smelting and rolling issues from the foundry. Once it is flat, I find the middle 1/16" and outline my grind pattern. I grind to the these lines so I have matching angle on both sides. It is easy to see if one side is 1/32" off from my grind line and to bring it where it needs to be. Sometimes 1095 can decarbonize in the open air forge so you need enough stock available to remove if this occurs and not loose shape.
Outlining the grind layout.
Here the center 1/16" is outlined
Filing groves in the thumbrest
Drilling holes in steel to pin the handles through

This is the finished grind on the blade before it is sent to heat treating out in my shed, which is located well away from my house. This is where your turn soft annealed steel to hardened steel. It requires heating the blade blank then quenching it in oil.

This requires scientific knowledge and welding gloves. When high carbon steel reaches the correct temperature it becomes non-magnetic. I have a magnet on my forge station that I test with. Once it reaches non magnetic stage, I soak at that temperature in the forge to ensure proper heating. Then you take the red hot steel and instantly plunge it into the oil. At this point the oil catches fire and the blade is rapidly cooled and hardened to somewhere around rc70 and to brittle to use. Now comes the crucial temper process. 
To temper the steel you use the correct chart of time and temperature that will produce your preferred level of Rockwell Hardness (rc). This temper will turn your brittle steel into usable knife grade steel. Here are the two blanks that used to be shiny and have been oil quenched and now tempered to around 60rc.

Now comes the tough part in making a knife, finishing the grind, fitting the handle and polishing. Do you want a mirror finish or something for the field?

These knives have about 10hrs of labor invested so far and aren't quite halfway.

The one on the left will be a gift between warriors. My personal blade is on the right.

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