The "Ask Nathan a Question" Thread

Hey Nathan the Machinist Nathan the Machinist !

I just saw the upcoming friday sale. I just wanted to ask the hardness and behind the edge thickness of CruWear variation of the knife. It would be great to have that knife in CruWear if it is harder and thinner than delta3V version.

As you do not usually make knives in CruWear, it would be great (if you could of course) to have side to side comparisons with delta3V, like the video you did with MagnaCut for DEK1.

For me the selling point of CruWear would be the edge stability at higher hardnesses (i.e. higher toughness at higher hardness compares with delta 3v). With regular knife specs. (i.e. thick geometry-20 tho behind the edge- and 60.5 HRC), I do not think CruWear has much more to offer compared with delta 3V other than reduced stain resistance and bit bump in wear resistance.

Thanks :)
 
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Nathan the Machinist said:
Powered grinding can easily burn the very apex of the edge. Delta protocol is more sensitive to this than most. It does not take much to lose the structure that gives us the properties that we want at the very leading edge which is where it really counts.

I do sharpen powered, but the belt is moving slow enough you can read it, and it is dripping wet. Places that sharpen with powered grinders will tell you "don't worry the edge doesn't even get hot". They don't know wtf they're talking about.

I did the math once and I found that you could raise the temperature of the leading .005" edge to 1,000° and it would cool off into the blade before you could touch it and it would not raise the temperature of the blade by 1° . You would never know that you burned it, and you wouldn't understand why your edge retention isn't right.

So I strongly encourage people do not use powered grinding on Delta 3V. I do it, but I'm doing this in production. I'm doing it at low speed and under flood coolant. Most places doing powered sharpening are not doing it right. And it's perfectly fine for a production knife with a shit heat treat, but you do not want to subject a CPK to that.
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Am I to assume you're using a low tempering temperature, or would that be an incorrect assumption (wouldn't be my first, lol)?
 
HPD said:
Am I to assume you're using a low tempering temperature, or would that be an incorrect assumption (wouldn't be my first, lol)?
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Nate's described the D3V heat treat protocol they developed, as their 'low temp tweak'. The exact process is obviously proprietary, but one of the things he's mentioned was to avoid subjecting D3V to 400f or higher IIRC (which is something that might happen if the owner sent a knife out for DLC coating, etc.)
 
bluemax_1 said:
Nate's described the D3V heat treat protocol they developed, as their 'low temp tweak'. The exact process is obviously proprietary, but one of the things he's mentioned was to avoid subjecting D3V to 400f or higher IIRC (which is something that might happen if the owner sent a knife out for DLC coating, etc.)
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My bad. I didn't ask the question properly. What I meant to ask was is it safe to assume that he's using a low temperature within the low temperature range, meaning something like 300 or 325 F instead of 400 F?. Thanks for the reply! Everyone recommends 400 F, including Larrin in his book, but I'm thinking of reducing my Aust. temp to reduce retained austenite and using a lower tempering temp. to keep the hardness up. Obviously this would require more care upon final grinding and shaping of the cutting edge.
 
If someone wanted to make field sharpening boards with sand paper to be used on CPK knives, what grit succession would you recommend to get a chipped blade back to not noticing the chip was there? And how do you feel about micro mesh for the same application?

Thank y’all for your time!
 
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