Informal ZDP-189 test

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bgentry

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Aug 3, 2009
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I've done a couple of quickie tests with my new Delica FFG in ZDP-189 and wanted to share and ask questions.

I cut cardboard with the Delica in FFG ZDP plain edge, another Delica in VG-10 SE, and a razor knife with a brand new blade. I wanted to see what the relative differences were between them. Understand that this was very quick; less than 10 minutes per test, very informal, and not at all scientific. Even so, I found it interesting.

For the first test the ZDP blade was basically as from the factory. It had cut paper and shaved hair, and I polished it on a loaded strop for a few minutes to make it sharper. It cut cardboard well, and the FFG blade seemed to have less resistance through cardboard than the saber shape of the VG-10 SE Delica. Cardboard varies a lot and we sometimes get this kind that has a thick profile, but the material itself isn't rigid at all. It's kinda floppy or spongy. So starting a cut on the edge of one of these pieces, the ZDP blade tended to fold the material over, while the SE blade, with a slight pull, began the cut and zipped through it.

Using a penetrating cut first (the tip through the side wall), the FFG ZDP blade was clearly better than the VG-10 SE. The later seemed like it had tons of resistance, which I attribute mostly to the blade profile, as opposed to sharpness or the fact that the VG-10 blade is serrated.

Using a razor knife it became clear that "thin wins" in this test. Clearly the least force used and the easiest to make a cut with. Though the FFG blade was surprisingly close! It really zipped through once it was in; much like the razor knife.

I did two testing sessions over two days and I stropped the ZDP and VG-10 blades in between until they seemed very sharp (hair shaving and cleanly paper slicing). Here's what surprised me the most: The ZDP blade lost it's shaving ability almost instantly. After 5 or 10 feet of cardboard it would *barely* and mean barely shave on day 2. Just catching a hair or two. It still seemed to cut pretty well, but the fine polish was gone.

Now again, the ZDP edge is mostly factory, just with the microbevel stropped to hair shaving levels. I'm trying to figure this out, as I've seen our member here, Unit and his video of slicing the side walls of tires and then shaving arm hair with his ZDP blade (can't remember which one but I think it was a Stretch). I've seen another member here CrimsonTideShooter cut hundreds of slices out of rope with his ZDP blade and then cleanly cut phone book paper.

My guess is that if I fully polished the entire edge, and not just the microbevel, it might do better. But I dunno.

I look forward to comments.

Thanks,

Brian.
 
I did two testing sessions over two days and I stropped the ZDP and VG-10 blades in between until they seemed very sharp (hair shaving and cleanly paper slicing). Here's what surprised me the most: The ZDP blade lost it's shaving ability almost instantly. After 5 or 10 feet of cardboard it would *barely* and mean barely shave on day 2. Just catching a hair or two. It still seemed to cut pretty well, but the fine polish was gone.

Now again, the ZDP edge is mostly factory, just with the microbevel stropped to hair shaving levels. I'm trying to figure this out, as I've seen our member here, Unit and his video of slicing the side walls of tires and then shaving arm hair with his ZDP blade (can't remember which one but I think it was a Stretch). I've seen another member here CrimsonTideShooter cut hundreds of slices out of rope with his ZDP blade and then cleanly cut phone book paper.

My guess is that if I fully polished the entire edge, and not just the microbevel, it might do better. But I dunno.
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The downside to trying to polish a micro bevel is the fact that it's 'micro' (very small). Any variation at all, in the angle or in applying pressure, will have an immediate and detrimental effect on the edge. Angle & pressure would have to be absolutely perfect from start to finish, in order to avoid degrading the micro bevel. If you do want to polish, it's much easier to do it with a wider bevel, as the bevel itself will help stabilize angle & pressure. Micro bevels are fine, but they're best applied in only a few very light passes (for me, less than 5 strokes per side; maybe only 2 or 3).

I'm betting you might've had a bit of a burr or wire edge on your micro bevel initially, which would shave very nicely. But it folded (or chipped off) as soon as it encountered tougher material. That's why the 'shaving edge' degraded so fast, most likely.
 
When I say microbevel on this particular knife, I mean the tiny little polished edge that it came with from the factory. I've been told here that this is from the buffer they use to remove the burr at the factory. I stropped the edge after playing with it some, before doing any cutting of cardboard, because it shaved roughly and I thought I could make it better without really affecting the edge much. I definitely didn't affect the primary edge.

...and I definitely made it sharper. I don't think it had a wire edge unless 5 minutes of slow to medium paced stropping on compound created one. Again, if so, I must have recreated that wire several more times as I stropped it between cutting sessions. Also, before my last round of cutting tests, I ran the edge through the end grain of some pressure treated lumber 2 or 3 times.

I'm not rejecting your explanation entirely, but presenting evidence for why I don't think it's necessarily correct.

Anyway, as of yesterday, it's doing exactly the same thing. Stropped it Friday night to hair shaving, cut 10 or less feet of cardboard on Saturday, and the hilt and middle no longer shave hair. Still cuts cardboard nicely though.

I was going to use this blade in "factory trim" until it got noticeably dull while cutting and then put on a 15 degree (per side) primary bevel. Later I planned on reprofiling down to 10 or 12 degrees per side. This early loss of shaving edge makes me think I should just reprofile it today and not bother testing this factory edge any more. This is really puzzling.

Thoughts?

Brian.
 
As you found blade geometry plays a big factor in cutting ability and often has a bigger effect than sharpness. The razor is a good example of this, a razor is thin but also has the proper bevel configuration to cope with the uses its put through. If you look closely you will see the bevel of a razor is cut very low and with a coarse grind followed by a micro bevel with a very high polish. The main grind being cut so low keeps friction low due to the lower transition angle between the bevel and main grind. The microbevel brings the strength back up in the edge while also bringing a high degree of sharpness, the really sharp point followed by flowing shallow angles and thin stock make a razor perform.

Now, the edge issues you are having with the ZDP is likely because its a coarse factory edge and not very well done. Sure it may be sharp but its not like it should be for the type of steel. ZDP is a high performance steel that needs a high performance bevel, I would recommend waterstones to around 8k or higher.

Stropping after each use will bring back some sharpness but it will also be duller each time you do it. Trying to work with a factory edge is like playing darts in the dark, you don't really know how its going to turn out. On top of that you are breaking one of the first rules of sharpening, don't create large gaps in your grit progression. Carefully sharpen then try again, you will probably have much different results.
 
Anyway, as of yesterday, it's doing exactly the same thing. Stropped it Friday night to hair shaving, cut 10 or less feet of cardboard on Saturday, and the hilt and middle no longer shave hair. Still cuts cardboard nicely though.
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That speaks for itself. I still think your shaving-sharp edge is actually a wire. Factory edges aren't supposed to have them (ideally), but they frequently do, nevertheless. It's likely that your stropping hasn't created a wire edge, but I think you still have some remnant of it there, and stropping keeps re-straightening it, so it'll shave again (briefly). A quality shaving edge, if it's truly good and clean, and supported by good bevel geometry, won't quit that fast on a high quality steel like ZDP. Wire edges, on the other hand, do fail in exactly that manner, because they're too thin to be strong.

Knifenut explained it well, in terms of how the geometry of the edge, and the bevel behind it, affects cutting performance. It does sound like the grind geometry behind your shaving edge is relatively blunt, once the wire edge can't function as a razor anymore. I think Knifenut's suggestion of re-sharpening to a better, cleaner and more uniform bevel, is what that edge needs.
 
Well that's two votes in favor of me scraping this factory edge. :)

I was considering trying to follow the factory grind and just polish the entire bevel down, but I don't think there's any point. ZDP is supposed to be killer to sharpen, but I'm just going to set it to 15 degrees and see how it performs from there. I'm guessing it's kinda close to that to begin, but I guess I'll find out soon enough.

No time tonight to do it, but perhaps I can do it in an hour or two some time this coming week.

Thanks for the suggestions and observations guys.

Brian.
 
bgentry said:
Well that's two votes in favor of me scraping this factory edge. :)

I was considering trying to follow the factory grind and just polish the entire bevel down, but I don't think there's any point. ZDP is supposed to be killer to sharpen, but I'm just going to set it to 15 degrees and see how it performs from there. I'm guessing it's kinda close to that to begin, but I guess I'll find out soon enough.

No time tonight to do it, but perhaps I can do it in an hour or two some time this coming week.

Thanks for the suggestions and observations guys.

Brian.
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I would love to hear how it went, because I have a ZDP delica and part of me wants to reprofile it, but I hear non stop about how the crazy rockwell scale makes it ridiculously involved.
 
I just received my ZDP Delica today and would also love to hear how this went - or any of the other sharpening afficionados' recommendations for what edge works best on this particular knife for EDC.

I know the question is "what do you want to do with it?", but I'm just looking for an all-around daily use edge- sturdy enough for zip ties, but also taking advantage of the properties of ZDP.
 
All the time, what would you like to know?
 
i like a one-question-one-answer guy. so, what arrangements do you set up (the sharpening surface, the sharpening medium, physical or visual templates in use, etc)?
 
I like to use waterstones on ZDP because they seems to cut fastest. Truthfully using the proper tools takes the pain out of sharpening this steel though it still will take longer due to hardness and alloy make-up.

Unless the blade is damaged, such as chipping or major dulling I typically use my 1k and 6k arashiyama stones. Because this steel has the ability to take such a fine edge 6k is still fairly toothy and aggressive in cutting. It takes a 8k or higher finish to start taking the tooth out of ZDP.
 
went through your links, btw. practically a complete lesson. my experience is more with minerals and a little of gemology. i was thinking i'd start with the fine side of the carborundum which will give me the primary "relief" or at least remove the factory grind. and i want a relief width no bigger than the original factory (20-20 degrees?) and then, i would go to a glass plate, first with perhaps 2-3 micron aluminum oxide or diamond and then with sub-micron diamond, all on the glass plate. i plan to tape "shoulders" on either side of the spine to make the angle consistent.

i don't plan to put a micro-grind to strengthen the relief.

one important question i have is grinding direction. with stones, i shape facets, or basically a flat surface against a flat surface. movement is just side-to-side. with knives i've always done it edge-trailing but some say edge-forward on a hard surface (not a strop) is faster and better.

thanks for the answers, and the ready links.
 
http://www.youtube.com/user/MrEdgy81?feature=mhee

That should be a link to my YouTube, MrEdgy81. I have a few videos that would probably answer many of your questions, particularly the 0550 and Les George vid's.

A steel like ZDP is good, I would take it to 15 per side. In reality though you sharpen lower and lower until the edge fails then you sharpen just above the failure point. This gives you the lowest possible edge angle the steel can handle with the greatest degree of performance due to the sharpened bevel being as thin as possible.
 
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