Kershaw Tyrade D2 edge deformation

S

snorkem

Joined
Aug 12, 2009
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I used my Kershaw Tyrade to cut a pine branch that was 1/8 of an inch in diameter and it suffered what i consider to be some very noticeable edge deformation. I don't have any pics but I'm sending it in to Kershaw for sharpening tomorrow.(I cant sharpen re-curves) I don't know if this is normal but it did not hold up like I expected. i have other knives that can take a lot, this one gets chipping/deformation when i whittle with it. Is this usual or do i have a lemon. And if this is usual then what is so great about D2, i had never used it before and now i know that
1. it damages easily
2. its hard to sharpen

I'm very disappointed with how this blade performed.:grumpy:
 
bad heat treat is possible since the branch was so small. i'm sure the guys at kershaw will find out the problem. i have a d2 blade thats ground real thin and holds up great. when you get a good d2 blade, you will love it.
 
CPM-D2 is not going to perform or sharpen anything like normal D2. At angles of less than 30 inclusive you will notice deformations and rolling. The gut feeling that the steel should be able to take more is correct and it can but it needs the right edge. Using a microbevel or a steep convex at around 15 degrees with medium pressure will make it perform the way it should. FYI, convex makes recurves easy.
 
I cant convex my own edges at this point, i have a few free hand stones and a dmt aligner. I just used the edge as it came from the factory. Do you know what the factory edge angle is?
 
Well, not really. From what I understand CPMD2 has much smaller carbides then normal D2 and you are able to sharpen at a much shallower angle and the blade should not chip. On normal D2 you can't sharpen very shallow or the large carbides will get ripped out when in use. This has been my experience in use too. I once sharpened a normal D2 knife with a 15 degree angle and it chipped like crazy. Sharpened it back to 20 degrees and it was fine. The kershaw leek CPM-D2 that I sharpened at 15 degrees doesn't chip and holds its edge very good.
 
i have a normal d2 blade that i made with a real thin edge and it holds up great. i gues it might depend on who does the heat treat as to how well it holds up.
 
richard j said:
i have a normal d2 blade that i made with a real thin edge and it holds up great. i gues it might depend on who does the heat treat as to how well it holds up.
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Yes, perhaps you are right because I hear that Dozier's heat treat of D2 is legendary. I was using D2 that was heat treated by benchmade made (Snody activator). It's just I have heard this argued many times over, but I have limited experience with normal D2. It's just my experience were very much the same as what I have read. But Dozier's D2 is apparently like another steel, lol.

Here is a picture of D2, notice the large chunks.

med_1181826854-D2.JPG



Here is a picture of S30V

med_1181826860-S30V.JPG
 
In testing some have commented on how D2 can 'seem' to deform along the edge and reflect light back to the user as if to indicate it is dull. I've noticed in my own testing of this steel both in knives I've made and in ones sent to me to test by manufacturers that in just a simple carpet remnant cutting test right after sharpening that D2 can seem to show a lot more light reflection back than others its tested against. What is the real tell though is whether it still cuts and in fact the perceived effort many times was actually less after using it a while right after sharpening than when the edge was seemingly more true along the apex.

The larger carbides can pull out of the matrix some during use and I suppose this is what is happening but what that actually seems to do at least with D2 is that it makes what amounts to a micro saw toothy edge that actually gets after it pretty good in use. Cliff Stamp and I had a conversation about this with both D2 and S30V and how when the trials for cutting were begun and after some deformation and light reflection was noted on both steels the effort to make the same cuts was actually less. So in research you could probably search out some of those old threads but what I'd say is that if by edge deformation you are looking down on the apex of the cutting edge after use and deeming it dull due to light reflection that with D2 and even S30V to some extent this is not necessarily a sure sign that the knife is getting dull. All steels will lose carbides when used.

Larger carbide means the spots along the apex will be easier to see which is why it may be the case that if you compare the D2 to a 13C26 razor blade steel that has small carbide size you may end up feeling like the 13C26 is holding up better than the D2 just simply because after the same amount of cuts in a carpet remnant the 13C26 edge reflects back less light to you in the sun. The reason may not be as apparent as it seems though in either the effort to make the cuts or in what is actually occurring. Both steels will be losing carbides as you cut but the difference would be in the micro size of one vs the other. Its simply easier to see on the larger carbide sized D2 steel what is happening in both steels and although the powder metal technology will look different in a microscope my understanding is that it simply more evenly distributes a more uniform sized carbide size throughout the steel to make a better blade in the end. The carbides are still large though and if you take the edge angle of any D2 blade beyond a certain point you will effectively weaken the edge to where you see micro fractures and chip outs. Consider it a sign that you need to make the edge stronger by making it a bit more obtuse at the bevel.

I never take my D2 blades beyond 18 degrees per side. In my experience 15 degrees weakens the edge too much but thats just my opinion based on use. From what I've seen its much more likely to chip when hitting bone at 15 degrees than it is at 18 or 20 degrees which is simply a better edge angle for that steel IMO. As someone else suggested it may be a good idea if you have a 15 degree edge bevel angle to follow that up with a secondary bevel of 20 degrees to strengthen the cutting edge. :thumbup:

STR
 
richard j said:
the factory angle should be 20 degrees. and d2 is d2 :rolleyes:
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The factory angle could be anything from 10 per side to 20 per side, it all depends on how they were holding it at the factory when they ran it across the belt. CPM D2 (the type of steel on the knife in question) is NOT D2 and as I stated earlier has different performance values and does NOT sharpen in the same way.

Straight from a Kershaw rep that I spoke to over the phone. AISI D2 with either, or combined factors of..... Rc above 61, this gives high wear resistance but at the same time makes the steel brittle. Low edge angles will cause chipping/deformations. I called to ask because of all the D2 is brittle talk and wanted to see what they said considering the abuse I've put my Outcast (AISI D2) through. I also found out the outcast has a lower RC of 57-58 and IIRC a spring like temper.

Acute edge angles seem to fair slightly better with AISI D2 than CPM-D2 but larger edge deformations will and do happen at lower angles with these steels. CPM-D2 will sharpen and polish with ease and take on extreme levels of sharpness that will make your straight razors jealous. Though the edge retention of CPM-D2 is on par with S30V its still a CPM steel and wears as such. Typically the sharpness is lost fast in favor of a toothy edge that as more wear occurs becomes increasingly dull to the feel but still cuts like a coarse edge knife. Another odd but interesting thing I notice in testing is how coarse materials like cardboard and drywall will tend to sharpen the edge of CPM steels. Not really sharpen them but once the edge gets "toothy dull" cutting these materials seems to have little further dulling effects.




CPM-D2 is also not made anymore, Kershaw seem to have bought ton's of it though as they are still producing knives with this steel.
 
Jason,

Since you feel that the CPM steels lose their razor edge somewhat quickly, what is a steel that you feel holds an extreme razor edge for longer? I have got to the point where I like my knives razor sharp so just curious what a good steel is that will hold it a little bit longer. It seems like most of my steels are CPM except ZDP189 so just wondering what you think will hold that really sharp edge longer even if it dulls overall more quickly.
 
Of the stainless CPM steels I like S90V the best and for the "carbon" side M4 seems to stay razor sharp forever (@62+Rc). CPM D2 holds a sharp edge longer than say S30V but for the average user the difference would be hard to notice. Elmax is another one that seems to be showing good ability to hold a sharp edge but thats still in "testing" and needs time before a confident conclusion can be made.

Outside PM steels I kinda like 14c from kershaw and whatever is on the mora2k.
 
O...and ZDP seems to hold it very well but the edge likes to chip when hard contact is made and I don't really like that quality in a edge.
 
Thanks for all the great Information, I am going to add this thread to my bookmarks because it contains so much information. I never knew there was such a big difference between cpm D2 and regular D2. and wow knifenut almost 5000 posts, thats a lot.
 
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