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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 03-02-2002, 02:18 AM
John Frankl
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edge geometry, edge testing, etc.


This is sort of a multi-part question that comes from developing different test blades. The latest, 5160 handled according to Ed's article, did some odd things.

Anyway, I am wondering first about the brass rod test. Does edge geometry affect it? IOW, will an edge that is tempered correctly still take a set if it is ground to thin? Also, if the edge is a bit too thick, will it fail to flex at all?

Next is on tempering temperatures. I am wondering if 350 is sometimes a bit high. I have been tempering at 350 but my edges seem a bit soft. Also, if I am only quenching 3/8 to 1/2 inch of the edge, does this affect tempering temperatures (as opposed to a blade hardened 1/3 to 1/2 of its width)?

Finally, could a slightly low carbon content--I know some steels vary by .01 percent or so--be giving me softer edges? And if I ordered this particular steel about 4 months ago would it be too late to get exact mill specs from Admiral?

Thanks,

John
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  #2  
Old 03-02-2002, 09:54 AM
Ed Caffrey
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Now your starting to get the picture!! WWAAAAHHOOO! I can see the wheels turning from here!!
I'm not poking fun.....I'm serious! The questions you pose are the ones that I wait to hear from young bladesmiths. It tells me that things are starting to click!
Anyway, I just got a little excited....I'm better now.

"I am wondering first about the brass rod test. Does edge geometry affect it?"
YOU BET! Edge geometry is just as importatnt as everything else, it must be "blended" with all the other elements to achieve "The Overall Package"

"Next is on tempering temperatures. I am wondering if 350 is sometimes a bit high. I have been tempering at 350 but my edges seem a bit soft. Also, if I am only quenching 3/8 to 1/2 inch of the edge, does this affect tempering temperatures (as opposed to a blade hardened 1/3 to 1/2 of its width)? "
If the edges are soft at 350F, it could point to a number of variables. I would first strart with the other processes in your knifemaking......proper forging, noramalizing, annealing, etc. Ensure that each step you have taken to that point is correct......again, each step in the process has an effect on the next step. This article on my site might help:
www.caffreyknives.com/top.htm

I would highly recommend that anytime you purchase steel, you demand to have a spec sheet sent with it! The reason I say this is that several years ago a company in the NW was selling what they claimed was 52100 in flat bar. I became suspicious, because 52100 does not come from any mill in flat bar, and there are only two sources I know that have it in the States (this place wasn't one of them). Just too see, I called and ordered some. I also asked for a spec sheet (which they told me they did not have.........RED FLAG) I got the stuff, and from the getgo, it did not look like 52100, nor did it feel like 52100. Then came the forging.........not even close to what 52100 feels like under the hammer! I made a couple of blades, heat treated them as 52100 and tested them........they were junk! Chipped edges, and would break at about 30 degree bends. I finally sent them off to be spectrographed........It came back as O-1! I called the company and complained. Their response? "Well, it's really close to 52100." My point being, unless you are a bladesmith, often times you do not understand the importance of those "minor differences" in steels. I doubt that it would do any good to request a spec sheet now. Spec sheet are generally engineered along with each batch of steel, and there are differences from batch to batch. You would likely just get a generic sheet. (If companies play the game as it should be played, spec sheets change with each new batch of steel, but most try to get by with a generic spec sheet, which doesn't help us much)
Sorry about getting so long winded, but when I see the light coming on with someone, it's time to celebrate!



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  #3  
Old 03-02-2002, 12:54 PM
John Frankl
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thanks


Ed,
Thanks alot. No need to apologize for length, the more information the better. And thanks even more for the words of encouragement. Just knowing I'm on the right path gives me what I need to get through a few more failures. Ed Fowler is also good to read because he is very honest about all the failures he had to go through to work out his specific methods. I'll begin as you suggested by tightening up all processes prior to hardening.

Would it hurt to temper a blade at 325 just to see if my 5160 is closer to .05 carbon than .06? I could always go back to the oven if it chips out.

Thanks again,

John
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  #4  
Old 03-02-2002, 01:46 PM
Ed Caffrey
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Re: thanks


If you don't already have one, get an oven thermometer first and check the temp of your oven. If that checks out OK, then got to the 325F temper and brass rod test. If you get chips, then up the temp by 25F, and try again. It will tell you when your right!


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  #5  
Old 03-02-2002, 07:52 PM
John Frankl
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oven thermometer


Thanks Ed.

I have an oven thermometer, but I'm going to get a second one to compare with. One good thing, even if the one I have is slightly off, it does let me know that my oven cycles in a very narrow range.

I'll keep at it.

John
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  #6  
Old 03-09-2002, 12:21 PM
Cyrus Chan
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thin edge


Hi John,there was one question that ,as far as I know was not answered yet. You asked if an edge which is ground too thin will pass the rod test? Well, I suppose that a blade that is tempered correctly will pass the test, no matter how thin it is. It requieres just less pressure to do it. If I am wrong on that please guys let me know. Regards, Cyrus
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