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Ed Caffrey's Workshop Talk to Ed Caffrey ... The Montana Bladesmith! Tips, tricks and more from an ABS Mastersmith.

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  #1  
Old 11-10-2001, 07:57 PM
JossDelage
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52100 Differential Heat Treatment - clay & water OK?


Hi,

I have a 52100 bowie / clip point fighter I want to heat treat. If possible, I'd like to do a differential heat treatment, and I was thinking of clay coating it and quenching it in water. Would that work?

Also, I have access to both an electric furnace with electronic controls and a gaz forge. The gaz forge would heat the blade to Tc faster, and I would have a better control of how long the blade would soak in heat. On the other hand, I would have a better control of the temperature in the furnace. What would people recommend?

Thanks,

JD

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  #2  
Old 11-10-2001, 09:53 PM
Ed Caffrey
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52100 and water.........


Hi JD!
Whenever I think of 52100 and water, I cringe! :x I suppose if a person is used to water quenching alloy steels, you might get away with it, but I would not feel comfortable doing it. I would much rather heat the blade and edge quench 3X .
I noticed you also mentioned "soaking" the blade. This is something is discourage folks to do. Soaking is unnessary, and can only lead to grain growth, wich in turn, will weaken a blade.
If you are set on hardening the blade via the clay method, pack the blade with 1/4" of clay everywhere except the last 1/3 of the cutting edge. Bring it up to where the edge is at critical temp, then IMMEDIATLEY quench in pre-heated, light oil. Prior to covering the blade with clay, I strongly suggest that you normalize it, otherwise you are likely to get some warpage on the edge when quenched.
Oil type and temp are important with this method............ a very ligh bodied oil such as mineral, veg. , or olive. Maybe even a light hydraulic fluid, pre-heated to 130-160F. Just keep in mind that oil temp of higher than 180F, and you are likely to not get full hardness.
Some folks have had, and do have great success with water hardening high carbon and alloy blades, but the risks are just too great for me to recommend it. Let us know what you decide, and how it turns out.
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  #3  
Old 11-11-2001, 01:17 PM
Joe Walters
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52100 can be water quenched, but if your experience is limited, and you'd rather make a useable knife than one filled with cracks, go with the oil quench described in Mr. Caffrey's post above. If you're hell-bent on the water-quench, you have to bring the whole blade up to temperature to avoid the cracks, and you have to be right at critical, too hot and bad things are gonna happen. The reason you need to bring the whole blade up is that the blade will first reverse-curve when it hits the water, and then curve back to straight and then continue curving a little more. Think that puts the blade under any stress? A hot spine will bend alot easier than one that's below critical, and this will really help to keep the cracks from happening (sounds kind of counter-intuitive, but the resistance of a cold spine pushing against the curve the whole time is alot greater than one that bends with the edge as it contracts and expands--the back should start freezing up before the edge pulls apart, but you have to experiment with how thick your clay needs to be. With 52100 you'll need a thick clay coat to keep the water off long enough (wrap some wire over the clay to keep it on the blade too). The shallow hardening 10XX steels, or w-1 work alot better with the water-quench because you have to get the edge under critical in about 1 second or else you won't get 100% martensite--good if you want to keep the back springy. Remember, you don't have to get your blade down to room temperature, you just need to get it below 300 degrees or so (we're talking water-quench here). After that, get the blade into the tempering oven ASAP and let it soak there, clay and all for at least an hour. Cracks happen post-quench too.

I'm assuming your blade is at or over 10" long. If you're dealing with a smaller blade, you won't see nearly as dramatic a curve imparted, and all of the stresses will be alot less, which means a greater probability of success.
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Old 11-11-2001, 02:11 PM
JossDelage
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Thanks. The blade is indeed smaller, and it's a clip point fighter where I want the false edge hardened too. That should prevent the blade from curving.

JD

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  #5  
Old 11-11-2001, 03:58 PM
Joe Walters
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it will probably still curve a little bit. Remember, curving isn't the only factor that causes the cracks. Sometimes, even when you do everything right, the blade will crack. The thicker you leave the edge, the better (leave it at least 1/16" thick).
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