zdp189 vs m4 (sharpening)

[Surfingringo]

I recently picked up a zdp Stretch and an m4 paramilitary. These are two of my favorite models and the knives have both seen lots of sharpening and use already in their battle for pocket time. I have, though, seen some real differences in how the two steels sharpen. I recently reprofiled both knives to 30 degrees and then added a small microbevel. Here is what I have observed....

First of all, I would not rate either of the steels as especially hard to sharpen. The zdp though, absolutely does require a few more passes...I'm not sure if that is because of wear resistance or hardness, but it is notable. The good news is that it seems to get extremely sharp with the extra work. The real difference that I notice between the two steels though is the TYPE of edge they take.

When I had both knives cleanly apexed at 30, I applied a microbevel with 1200 grit dmt diafolds at 40 degrees. Both knives were extremely sharp at that point and would instantly bite into the hair on my head on contact, but the edges were quite different. The edge on the m4 had FAR more tooth. The edge on the zdp189 felt far more refined (as if I had finished it on the medium, or even the fine, sm rods). I played around with multiple grits and found that at any given grit, I could get the knives to equivalent levels of sharpness but the m4 always had a notably toothier edge.

I'm not sure what causes the difference, but my best guess is that this is a result of the depth of the scratch pattern at the apex? Could the difference in hardness cause this difference or would it more likely be due to steel composition?

Anyway, I tend to like a toothier edge for most work so I often lean towards the m4 as my steel selection, but there are times when I like to carry a more refined edge and zdp189 is proving to be a good option on those days. The point of this thread is not to portray either steel as better than the other but to discuss and understand how they respond to sharpening, what types of edges they take and why. Any thoughts or experience?

[Bloke]

Hi Lance,

I don't own any M4 but I did reprofiled a ZDP Manbug to somewhere under 30deg with the intent of a 30deg micro bevel. I used a Lansky and the two finest diamonds till I had a clean apex and then worked through the three Lansky Arkansas the finest with oil and the others with kero but nowhere long enough to get a polished edge. It's very clean but not much brighter than the rest of the blade and very sharp. I didn't think to try it on hair at the time so can't say. It cut an empty cigarette tube cleanly at the time. Don't ask me why it's just a kooky thing I do. And it still cuts newsprint easily. I was apprehensive of sharpening as I had read of people having difficulty, but it sharpened easier than I expected.
That was about a month ago but I now have a SM and I'll put a micro bevel on it. I like the steel a lot! I've maintained the edge by stropping on balsa wood with 5micron diamond paste and bare balsa to finish. :)

[anagarika]

Hi Lance,

Glad that you started comparing these steels (and hopefully HAP40 as well)
I still have my GB M4 (solid liner, no 'Taichung' mark, supposedly harder) and E4 ZDP. Your observation is quite close with mine. My guess is that the high hardness of the ZDP causes the diamond bites less deep. ZDP also seems to like lighter touch, which will result definitely in smoother and higher polish given the same DMT grit. Comparing both, the M4 feels softer, and the steel is removed faster. I don't know how hard is the PM2 M4, but guessing it's a bit softer than my old GB.

I found (a bit OT, but relevant I guess ) that HAP40 is even a bit toothier. I'm having a harder time making it more polished. I guess I have to try 1 or 0.5 micron diamond paste. Even using green on washboard, it polishes brigthly but still too toothy for my comfortable shave.

[Ncmiked]

I think the difference you are noticing is because of the different compositions of the steel, while zdp is high in carbon it has lower levels of hard carbide such as vanadium like M4. Just a guess

[bearfacedkiller]

I can only speculate at the reasons but I can say that I love the edge it takes and it seems to hold onto a high level of sharpness very well. It is a very unique steel, that's for sure.

[Bloke]

I can only speculate at the reasons but I can say that I love the edge it takes and it seems to hold onto a high level of sharpness very well. It is a very unique steel, that's for sure.

Hi Darby,

This steel is very new to me and I too like it a lot! For the reasons you mention. I'm hopeful, I may get an even sharper edge with a 30deg micro bevel on the SM.

I've been a little unlucky with chips and the reason I re-profiled so early was I dropped it not long after I bought it, closed on tiles and it opened on impact and rolled, would you believe the very tip just enough to catch skin. I knew what would happen but tried to "strop" it straight on glass and about 4-8 thou snapped off. After I fixed it I had it open on the coffee table and it got banged against a set of keys and chip/rolled a tiny bit you can hardly see even with 10X Loupe. Interesting how it rolls/chips rather than chipping out right.

[Able Dog]

I have no experience with ZDP-189, but I can agree with your assessment of M4.

I have found it surprisingly easy to sharpen, and it takes a very nice toothy edge that has a lot of "bite" to it.

[Surfingringo]

I think the difference you are noticing is because of the different compositions of the steel, while zdp is high in carbon it has lower levels of hard carbide such as vanadium like M4. Just a guess

I considered that, but here's another data point. I have spent a fair bit of time sharpening lc200n and it too takes a very toothy edge off of the 1200 diamond, and I believe it is a finely grained steel without many carbides no? From what I have seen sharpening various steels I don't think this is purely a result of carbide volume. Doesn't zdp have a different kind of carbide? Chromium? Wonder if that is part of it?

[Ruarch]

Just bumping this thread because I am very interested in what you all have to say.

[Ncmiked]

I think the difference you are noticing is because of the different compositions of the steel, while zdp is high in carbon it has lower levels of hard carbide such as vanadium like M4. Just a guess

I considered that, but here's another data point. I have spent a fair bit of time sharpening lc200n and it too takes a very toothy edge off of the 1200 diamond, and I believe it is a finely grained steel without many carbides no? From what I have seen sharpening various steels I don't think this is purely a result of carbide volume. Doesn't zdp have a different kind of carbide? Chromium? Wonder if that is part of it?

From what I understand chromium is added to make the steel "stainless". I'm reading and trying to learn about steels, so pretty much I'm just speculating at this point.

[bearfacedkiller]

Chromium can be added to increase corrosion resistance as well as to create carbides for wear resistance. Usually anything over 12% chromium is considered stainless but this depends on the amount of carbon present. In the case of ZDP189 it has 20% carbon but isn't stainless due to the very high carbon content at 3%. Chromium can form carbides just like our friends vanadium and tungsten. In the case of ZDP it is rich in chromium carbides and is lacking free chromium which is what provides the corrosion resistance. I am not a metallurgist and this post more or less exhausted my knowledge on the topic. I hope this is correct. If it is not I hope somebody chimes in with a correction. :o

Lance, I am not positive but I believe that chromium carbides are softer than vanadium or tungsten carbides. Maybe that has something to do with it. Maybe what you are seeing is that the chromium carbides in the ZDP are easier to abrade than the tungsten and vanadium in the M4. ZDP189 has only .1 Vanadium and only .6% Tungston so I believe the carbides are mostly chromium. This is just a guess from someone who only wishes he understood all this stuff.

[El Gato]

I can only add my own personal experience but I have always, without exception, been able to obtain a more aggressive edge on a non-stainless high carbon steel blade than one of a higher chromium "stainless" steel, with the same sharpness results that Lance is finding. I sharpen most of my blades to 15 degrees per side with a 20 degree micro bevel, same as Lance. To me the difference is noticeable and is why I tend to prefer a high carbon tool steel over any "stainless" steel. I blame the larger percentage of chromium for the difference in perceived sharpness, and to me the difference is real.

I am sure there will be many who will disagree with this, and that's okay. But I will continue to enjoy my Super Blue, K-390, CPM 4V, and now Maxamet, Mules and leave the high chromium steels to those who like them. My experience in sharpening has been what Lance has found.

[El Gato]

Might this difference be the reason why Japanese chefs much prefer a straight high carbon steel blade over any stainless steel for their chef's knives? I don't know.

[Bloke]

Hi El Gato,

I like to do perceived cutting tests, probably because no matter how I try I can't cut anything with data.

I compared the perceived sharpness of a favourite bushcraft knife, a Roselli Hunter with a 3mm Krupp W-75 un-alloyed carbon steel blade with typical zero Scandi grind that I'd used to put a fine point on an 1 1/2" eucalyptus branch for the sole purpose of removing a little surface rust. When I finished I stropped in on a brown 3M abrasive pad and called it good. The point I'm trying to make is this isn't a pampered knife and as you may imagine hardwood tends to micro chip a zero grind.

I grabbed some very dense card board about 1/16" thick and my brand new ZDP Stretch with factory edge and made a few cuts, I swapped knives and did the same! Looking at the knives I'd think the Stretch would out cut the Roselli by a country mile. After a couple of cuts I'd probably take the Roselli! How it works I do not know but if there is a perceivable difference in cutting ability or force or whatever it's called on that particular piece of cardboard between these two particular knives it's minuscule! Such is my personal observation.

[dplafoll]

I have ZDP, M4, and HAP40. So far with my Sharpmaker:
ZDP gets a very sharp edge, and it's got great retention of that edge. I can't say how polished it is without more refined tools, but it's very good. It does take more work to keep that way, but it's not super difficult. However, a real sharpening requires diamond rods or equivalent.
M4 also gets very sharp and keeps it a while. However, it feels sharper when I'm testing them after sharpening.
HAP40 is probably as good as either one in terms of sharpness, but doesn't quite retain the edge as long. But, it also is probably the easiest of the three to sharpen for me. I basically just wave the knife at the SM and it's back.

My sharpest knives are my Mantra in M4 and my HAP40 Dragonfly, followed by the ZDP DF2. After that, the HAP40 Delica and my CTS-XHP Chaparral are comparable.
The Techno and Nirvana are outliers due to blade thickness and geometry. Super sharp, just not the same kind of sharp as the others.

[Donut]

I think the difference you are noticing is because of the different compositions of the steel, while zdp is high in carbon it has lower levels of hard carbide such as vanadium like M4. Just a guess

I considered that, but here's another data point. I have spent a fair bit of time sharpening lc200n and it too takes a very toothy edge off of the 1200 diamond, and I believe it is a finely grained steel without many carbides no? From what I have seen sharpening various steels I don't think this is purely a result of carbide volume. Doesn't zdp have a different kind of carbide? Chromium? Wonder if that is part of it?

The way I always figure it... a carbide steel is sort of like concrete (or crunchy peanut butter :p ). It has stones, it has... smaller stones, and it has something holding everything together. Carbide steel has carbides, then it has a softer steel holding the carbides.

I think the ZDP has a harder steel holding onto the carbides. It doesn't really seem to have really hard carbides or a ton of them, but everything is on the high end of the hardness scale. Some stones don't cut into ZDP as much as other steels (which would give you higher finish with the same stone).

[tripscheck'em]

Perhaps the m4 is toothier bc it's softer than zdp-189, thus being deformed more by the stone? Though that shouldn't matter on diamond.

My experience is that zdp-189 is far easier to sharpen than vanadium steels at high grits, like the Spyderco fine. It very well could be that I am a sucky sharpener, but i hate having to reprofile and refine an s30v edge after heavy use/damage. Getting their apex just right is a chore for me.

[anagarika]

I think the ZDP has a harder steel holding onto the carbides. It doesn't really seem to have really hard carbides or a ton of them, but everything is on the high end of the hardness scale. Some stones don't cut into ZDP as much as other steels (which would give you higher finish with the same stone).

This ^
I do observe ZDP has a higher finish over same grit compared to others, even M4. I don't have enough metallurgy to understand, my guess is it might be overall carbides volume, imagine more pebbles but the pebbles are not as hard as Vanadium carbides. Or the steel matrix itself is harder (Hitachi required their HT for ZDP).

[tripscheck'em]

I think the difference you are noticing is because of the different compositions of the steel, while zdp is high in carbon it has lower levels of hard carbide such as vanadium like M4. Just a guess

I considered that, but here's another data point. I have spent a fair bit of time sharpening lc200n and it too takes a very toothy edge off of the 1200 diamond, and I believe it is a finely grained steel without many carbides no? From what I have seen sharpening various steels I don't think this is purely a result of carbide volume. Doesn't zdp have a different kind of carbide? Chromium? Wonder if that is part of it?

Yes, zdp is chromium based, no vanadium, but the diamond should cut that and vanadium equally.

Diamond stones are very sensitive to pressure bc they cut so aggressively. It could be that you pressed just a little harder and didn't know.

[harronek]

OK,

This is total " Bro Science " and anyone with some knowledge of that will understand these findings .
This is a compilation of my deluded musings .

ZDP189 -

Never did get it " nasty " sharp but boy did it work as a EDC blade steel in my working world . I experienced micro chipping early on which gave me reservations about this steel , but once I gave it a major re-bevel those dramas never seemed to reoccur . I own four ZDP 189 Spyderco's and this scenario has repeated itself on all of them , maybe its something to do with the factory grind ?
Please remember this is " Bro Science "

M4 -

Gayle Bradley GB1 " The one knife to rule them all " .
My only exposure to this steel .
My displeasure of the GB2 is based on the fact that the GB1 was in theory designed without compromise .
I carried the GB1 for a number of months , during that time I realized that without major alteration to my technique I was achieving sharpness not seen before .
There is an unspoken realm of " Sharp " that is never really mentioned on these forums .
When you no longer " Pop " hairs , " slide " through paper , " decimate " cardboard , " Impress " the girl next door , but you still " get stuff done ".
M4 kept me in this realm with the least amount of effort .
Please remember this is " Bro Science " .

As a working Steel M4 just ticks the boxes , " Bro Science " doesn't take into account corrosion , available models etc , but it does take into account real world , on the ground , user observational reviews .

Either Steel is happily included in my arsenal , but if you pin me to the wall and demand a option , it is M4

Ken

PS - Don't get me started about Hap40