Sharpening Stainless Steel and Japanese High Speed Tool Steel
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I don’t have the ability to quantify the depth of the scratches.
By depth, I meant from the edge into the blade, not from the surface. If your microscope software has measurement capabilities, you could check that. It would be interesting to try and eliminate some variables and test it again e.g. preparing a toothy edge and cutting a given material a set number of times and then repeating with a polished edge and measure the edge deformation, chipping etc…
-Clay
Marc, It sounds like you need need to invest in some better microscopes!
David, I see a SEM on Amazon for just $12,260. I think that one’ll work.
Marc
(MarcH's Rack-Its)I never looked at it from that point of view.
Now it’s in the morning here again (I wrote this pretty late last night) I realize I indeed never looked at it from that point of view, because I don’t understand. How come an edge suddenly becomes 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.
Do you understand how this phenomenon occurs, Marc? Or anyone else? (Ken, you wrote you had seen this before with high carbide steels.)
Molecule Polishing: my blog about sharpening with the Wicked Edge
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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.
Marc
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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!
Molecule Polishing: my blog about sharpening with the Wicked Edge
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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.
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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.
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!
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.
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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.
Molecule Polishing: my blog about sharpening with the Wicked Edge
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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.
Marc
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