Very thin, high hardness D2

Nathan the Machinist

Nathan the Machinist

KnifeMaker / Machinist / Evil Genius
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Very thin, high hardness D2

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This was a special request, he wanted one that was quite thin. A lot of my personal knives are this way, but I've only ever sold one other that was this thin. It has a high hollow grind with the tangent of the grind about .100" above the edge. It measured just under .010" at the edge and it doesn't reach .020" until pretty far up there. So it is starting to get into the same neighborhood as a straight razor with a belly on it. I sharpened it to about 25 degrees total included angle. It measured HRC 62

Obviously it is relatively fragile and wouldn't work well as a general purpose knife, but that's not what it was made for.

To me, knives like this are a lot of fun to play with. You can shave your face with it without touching the skin. You can cleave a grape dropped onto the edge. You can wave it around and split oxygen atoms. ...Okay, maybe not that last one....
 
Very cool, I'm with you on small knives being thin. I figured if I need to chop or prior on something I'd get a different tool. What's the intended use, doesn't appear to have enough belly to be a skinner? What are the overall dimensions? Once again, very nice.
 
"You can wave it around and split oxygen atoms."

So thats how O1 is made. :D

Nice knife my friend.
 
R. Mark Lee said:
Very cool, I'm with you on small knives being thin. I figured if I need to chop or prior on something I'd get a different tool. What's the intended use, doesn't appear to have enough belly to be a skinner? What are the overall dimensions? Once again, very nice.
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Blade is 3 5/8", 7 3/8 OAL.

It is a skinner. I put all the belly towards the tip. I don't like a fat skinner. Like many hunters, I don't split the pelvis, so a skinny blade is helpful in reaching in to disconnect the intestines and reproductive bits up inside the pelvis without severing any of it.

There are a lot of different approaches to processing a deer, ranging from: burry a knife into the gut, pull everything out, rinse with a hose and cook it well, to a more surgical approach. I do it the second way, so I lean more towards a scalpel in my preference in skinning knife.

I think "skinning knife" is a bit of a misnomer. I mostly just pull the skin off.


Don't get me started on gut hooks.... :rolleyes:
 
It's actually going to start off in the kitchen to get used to it, in the fall should make a great skinner, Thanks Nathan for making this one thin.
 
woodysone said:
It's actually going to start off in the kitchen to get used to it, in the fall should make a great skinner, Thanks Nathan for making this one thin.
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You bet Martin, it was fun.

I actually have a few in the kitchen. One is my personal skinning knife which is also thin like this. It lives in the kitchen when I'm not hunting. It does well in meat and vegetables and I've even run it through the dishwasher (I'm going to knife hell, I know).

My wife and I both use "screw ups" as steak knives. Hard D2 is a pretty good steel against porcelain. It doesn't blunt too bad and its toothy nature gets the job done. I really kind of miss it when I'm at a restaurant and have to saw up steak with a dull serrated steak knife.

I hope you enjoy your knives.
 
Hello Nathan,

Thanks for the dimensions. I have a "very" similar knife that is my hunting knife as well. I tend towards small knives since my dad taught me to field dress whitetails with a sodbuster style pocket knife. I never understood the need for a gut hook either or a large knife to tackle game. Your right about skinning deer, it's mostly pulling it off, especially if their still warm.

How does the thin edge at that hardness hold up to normal daily slicing and cutting? I guess I'm trying to say is what does it take to chip the edge? Will it hold up to light chopping, say veggies on the cutting board? I like thin blades, but have never tried on that hard, usally down in the 58-59C range.
 
R. Mark Lee said:
Hello Nathan,

Thanks for the dimensions. I have a "very" similar knife that is my hunting knife as well. I tend towards small knives since my dad taught me to field dress whitetails with a sodbuster style pocket knife. I never understood the need for a gut hook either or a large knife to tackle game. Your right about skinning deer, it's mostly pulling it off, especially if their still warm.

How does the thin edge at that hardness hold up to normal daily slicing and cutting? I guess I'm trying to say is what does it take to chip the edge? Will it hold up to light chopping, say veggies on the cutting board? I like thin blades, but have never tried on that hard, usally down in the 58-59C range.
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I think you would be pleasantly surprised with that kind of use. So far, I have always tested a blade to destruction from every batch. I will probably stop doing that if I ever stop tweaking my process. I have not abused this particular knife, but a knife from this batch did cut a nail in half with absolutely zero edge chipping. Just a small shiny flat spot in the edge. Mind you, that edge was .020".

Due to the low tempering temperatures used to achieve this hardness, my concern has been retained austenite. D2 can be counterintuitive in this respect, but the issue I have to keep an eye out for is not chipping, but edge roll. D2 at HRC 62 can suffer excessive edge roll. And D2 at 58 can be chippy (larger carbides and weaker martensite). It can be backwards from what you might expect.


This knife, at HRC62, chopped up ironwood without chipping. But it did suffer edge roll.

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If you were to pop this blade against a cutting board, you won't see much edge damage. The edge damage you will see will be roll, not chipping.

I use these things abusively, and have never had a serious chip.

In my cutting tests against cardboard, leather and hardwood, these knives have out performed every factory knife I have tested including some big names in VG10 and S30V. The only knife I have tested that outperformed these in my cutting tests is a custom in W2 made by a master. And I'll tell you, it was close.


I can say, with complete confidence, that these knives at this hardness are not weak. I send these thin knives off with a warning not to abuse them. But the reality is, my personal skinner is just as thin and I have abused mercilessly.
 
Thanks Nathan, that's very helpful information, and I'm very impressed with the abilities of your thin blades. Now I have to go read up on retained austenite versus large cabides and weaker martensite in D2. One last questions ... what tempering times and temps does it take to get HRC62 Vs HRC58 for these thin blades?
 
R. Mark Lee said:
Thanks Nathan, that's very helpful information, and I'm very impressed with the abilities of your thin blades. Now I have to go read up on retained austenite versus large cabides and weaker martensite in D2. One last questions ... what tempering times and temps does it take to get HRC62 Vs HRC58 for these thin blades?
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To answer the question, the tempering times are typically twice at two hours. But that is pretty standard across the board. Some HSS are three. And the temp is about 450-475

But, it is the austenitizing times and temps (which dictate the amount carbon in solution), and the tempering temps that get you to 62. And it is the quench rate and tempering temps that dictate what happens to that carbon. But it is the timing of cryo that addresses retained austenite when lower tempers are used. I give my D2 recipe to other knifemakers freely (I did just tonight, in fact), but I don't want to post details here.

I will say that the type and amount of carbides formed, the corrosion resistance, and the fine edge stability can be very different in two different blades that measure the same Rockwell hardness. That RC number isn't the whole story. At least with D2, which is the only steel that I claim to be an egg-spurt...
 
Cool knife and cool thread. I really like D2, it is what my edc is made of, but it is not ground that thin. I really like the handle scales, looks like some more of that nice osage orange!
 
Thanks again Nathan I appreciate the feedback. I am not as well versed as I would like to be on my phase diagrams and the different techniques need to produce a desired outcome for a given steel. I need to read up on this some more and do some of my own testing to help me better understand what I'm doing during the heat treat process. Once again, good looking knife!
 
I really dig this knife, Nathan. It looks comfy, handy, and it's got a nice pointy/sexy blade profile. Grinds and finish look excellent, and I bet it's a great slicer!
 
Thank you folks for the kind comments.

Tai,
That means a lot to me coming from you.
 
Nathan the Machinist said:
D2 can be counterintuitive in this respect, but the issue I have to keep an eye out for is not chipping, but edge roll. D2 at HRC 62 can suffer excessive edge roll. And D2 at 58 can be chippy (larger carbides and weaker martensite). It can be backwards from what you might expect.
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That's very interesting. I appreciate you sharing your experience with us.

I had a long phone convo with richardj earlier today; we were talking mostly about the fact that we both like really thin edges for cutting performance, and that it's possible to make such an edge that's plenty strong. I've never quenched anything yet, but my tempered Nicholson file knives take a heckuva lot more abuse than most of the production knives I own made of similar steels, and I grind the edges VERY thin. They're not difficult to sharpen at all, partly because even when they do start to get dull, the edge is so thin, there's not much to sharpen away. And I have yet to break one. (I haven't tried using a cheater bar )

I'm beginning to understand that HT is about much more than just a Rockwell number.
It seems to me that the "standard" 58RHC number I see all over isn't the be-all/end-all the factories would have us believe.

Sorry for the thread-drift. :o
 
I make my standard hunting knife from D2. I do my HT real close to Nathans. I was showing a guy how sharp it was etc. He asked how it would do if he wanted to split an elks brisket by hammering on the spine. I went and got a 16 penny nail, a hammer and a piece of aluminum. Laid the nail on the aluminum plate and set the knife's edge on it wacked the spine with the hammer and handed him the 2 pieces of nail and the knife.You couldn't even feel a nick in the edge. He kept it. D2 makes a poor spring and a great blade.
 
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