Mark I can only summate based on what I’ve read that the carbides being so large are being pushed out by the narrow grit stone as it attempts to thin the edge more and more. Actually my guess is the large carbides are getting broken out of the steel matrix by the edge leading strokes.
I realize I’ve posted some of this before, but I’m very curious how an edge can suddenly become rougher/chippier as the stones get finer? Is it because the edge gets thinner and narrower? I find this difficult to understand, since the low grit stones remove much more steel than the high grit stones; so comparatively they make the edge much thinner than the fine stones. Is there a tipping point regarding edge thickness beyond which the edge suddenly starts to chip? It could be, but I’ve never heard of it.
All information and tips highly appreciated!
At one point, I had an 800-grit stone(s) that produced some ugly chips in the edge of my ZDP Delica. It turned out that there were clusters of diamonds which were oriented longitudinally. This orientation proved to be very resistant to attempts to “break in” the stone. While the rest of the stone was broken-in beautifully, this (or these) cluster(s) would cause some really ugly results. Here’s a microphoto of the cluster:
I resorted to “sharpening” a piece of 1/4" plate glass. Within a few strokes, the clusters were banished.
Tom, what stones progression are you following to sharpen the ZDP Delica, these days?
It depends on the amount and type of damage. I had been sharpening to a 17 dps main bevel with a 20- dps microbevel, but I finally decided that the ZDP is too brittle for 17 dps. My Stretch in ZDP developed a deep chip which required a flattening of the edge down to the bottom of the chip. I had to go to my 400 grit diamonds to get back to an apex. In most cases, I had been using my 800s to get an apex.
I don’t think I’ll ever be able to justify the cost of a Maxamet Spyderco, but I’ll be real interested to hear how brittle they are.
Hey Mark, I don’t think that some harder steels can be refined as much because of the materials mixed with the steel to harden it. These materials will separate from the steel when the refinement gets to a certain point. It’s not necessarily the stones, all though as Tom stated that has to be considered, but the steel its self separates because it just can’t hold together after a certain point. They’re improving and advancing the steels faster than ever and some work better than others but like most things only time will tell which are “super” and which are not so super. There is also the problem of sharpening hard steel because the harder it is the less ductile it is and will just break out so the narrower it gets, and it won’t bend, it breaks or chips if you will. With every new steel the heat treating and tempering takes a while to find just what works best for that particular steel. They’re able to make finer grain steels now that do hold together better in a more hardened state but hardness and ductility will always be a trade off.
Don’t know if that was really your question or if it helped at all. Just my observations.
Thanks, sksharp, that ductility sounds like a good hypothesis. Although I still wonder why there is such an apparent “tipping point”. Once I can sharpen again (broken arm now) I will observe my edges through a microscope more routinely.
Sorry to hear about your arm Mark. I hope it heals quickly and completely.
[attachment file=“Left side just back from tip.jpg”]
For those of you that are frequent Forum readers, contributors, participants, regular readers and lurkers (no negative connotation implied), you have seen this thread brought back to life from time to time. You know I have an interest in what I have come to affectionately term " Super Steels, (SS)" or “Super Hard Steels, (SHS)”. When I find a new knife made of what is touted to be one of these newly contrived “SS” I usually have to buy it. Well it’s happened again. My favorite knife importer described in their newsletter one of these special beasts.
It is an 8" Chef’s knife make by one well-known Japanese Master. The steel is “HAP-40” and is supposed to possess the cutting ability and edge retention of ZDP-189 or Aogami Super with better toughness than ZDP-189 at HRc 68.
I have photographed the “out-of the-box” edge with the USB microscope at 250X of all of these newly purchased super star steel knives. I try to record the edge to use and emulate the sharpening style and grind in order to sharpen these knives like originally done. I use these knives for as long as I’m able to with their “out-of the box” edge until they no longer perform well enough to continue to use enjoyably.
This practice has allowed me to become more familiar with the cutting, handling and durability characteristics of these knives. I used to sharpen all my new purchases as soon as I got them. I learned all I was doing then, was using one of Marc’s sharpened knives. Not using a knife made and sharpened by a Master. Using them first, I hope to have a good basis of comparison, and a recollection of the knife’s cutting ability.
I have also been surprised by how well these knives cut and handle with what appears to be a fairly rough and unimpressively sharpened bevel. The bevels are often quite rough or coarse and uneven with very little attention to detail. This led me to re-examine my sharpening theory when dealing with these “SHS” knives.
Here are several bevel shots of my latest purchase. The attached photos are described as the knife is clamped with bevel up orientation. As these knives wear and require sharpening I will share my experiences and attempted techniques employed to attain an edge comparable with the Master’s original.
Man, that gives new meaning to a toothy edge.
The knife is a surprisingly good cutter/slicer. It has a very thin overall geometry, that is thin behind the edge and then all-the-way up to the heel. It is very light for its design. David, as you remarked, I truly was surprised how well it cuts considering the toothiness of the original sharpening job. It definitely will make you re-evaluate your thinking on what is necessary to have a sharp knife. Cause and effect, or bevel grind VS cutting ability is the driving force behind this thread (study). I’ve learned the edge doesn’t have to look good to perform well!
Thanks, Marc. As you may know, I am particularly interested in kitchen knives. I have been eyeing knives in HAP-40, but never bought one. (They’re not cheap…) Maybe in the future, but I’m very interested in your experiences, both when you use it sharpened roughly (like now) as well as refined.
I am not surprised the knife cuts so well now. When I sharpened for a restaurant there were chefs that didn’t want me to go finer than 800 grit. The tooth do help and the knife keeps its level of refinement longer.
You wrote about a newsletter describing the knife. Would it be possible to email that to me (or to post it here if it’s not too off-topic)?
This is a video, posted in July of '16, of a Japanese Aritsugu knife my sister purchased as a gift for me at their store in Kyoto. They sharpen in two stages. First, a master hones the edge on an abrasive drum in a direction parallel to the edge. Next, another master puts the final bevel on by the traditional waterstone method, perpendicular to the edge. If you watch the video, you’ll see that there are a lot of minor defects on the edge. The video was taken before the knife was ever used, so the defects are just a part of the knife. It’s incredibly sharp, but this seems to be a result of the very low bevel angles. From what I could see without actually touching a stone to the edge, the edge was convex sharpened to 12 degrees, inclusive. The edge is so thin, you think of foil, or the flexible edge of a straight razor.
Tom, has the edge stood up well with use? It looks like it would easily roll. It is quite thin.
12 degrees inclusive? Wow! It looks much cleaner than the edges on the knives that Marc has posted, I bet it just glides through veggies.
That’s an impresive video, even though there are some defects on the edge. I have the same question as Marc and Organic: how does the edge keep up? Or is the knife only used for specific goods, say, relatively soft vegetables?
I’ve only used the knife a half-dozen times, and haven’t checked it with the 'scope since. I’ll try to do so in the next few days.
Yes, I’ve only used it on soft veggies like tomatoes. And it’s so incredibly sharp you wouldn’t believe it. Wheeee! It easily does the paper-thin tomato slice Mark showed us.
Here’s a video about sharpening maxamet steel that I think is relevant to the conversation:
[youtube]https://www.youtube.com/watch?v=3jaURPyoJz0[/youtube]
Thanks. That’s very interesting, particularly that Spyderco makes the edge quite coarse (150 or so, the guy said) and the microbevel very polished. I usually do it the other way around. And he has the same sharpening experience (chipping) as some people here 
.
Great knife, by the way. I was saving for a Paramilitary in Maxamet, but I think I will now save for a Manix 2.
[Edited: I mixed up topics.]
Mr. David, Thanks for posting the YouTube video. It was very interesting and informative. It feeds right in with my experiences that drove me to start this Thread / Topic in the first place. Maxamet is just one more of the what I choose to call “Japanese Super Steels”, (JSS), to add to the list of steels with the disappearing edges while sharpening. I don’t feel so bad anymore, hearing there are others out there, that have repeatedly experienced similar issues, as I have, while sharpening these JSS. I find it particularly interesting the counter-intuitive methods tried and ultimately utilized to overcome sharpening difficulties with these steels. His referring to the Maxamet steel, and all the JSS, for that matter, as more ceramic-like then steel-like is a great analogy.
One problem I see is there is a limited production and use of these JSS due to the high price points. It makes me wonder is it worth the expense and inconvenience to buy and try to use and sharpen these JSS. Maybe the steels or the methods of making these steels is just in it’s infancy and is evolving till the makers get it down. I guess we’ll see in time.