Mike, I like to think sharpening Japanese chef’s knives is my area of experience. I like to collect them, I regularly use and sharpen these types of knives. The issue with them is there are so many different kinds of steels, both stainless and non stainless, and different steel hardness. These steels can vary greatly in how well or easily they can be sharpened. There is no rhyme or reason or general rules to apply to the different steels, but I’ll try to summarize or give generalities where I can. The discussion of Japanese Chef’s knives can be long and involved because there are so many different knives of different styles for different uses, made from a large variety of different steel. (I tend to get too deep into the discussion, also.)
High Carbon steel is generally used as a term to categorize the non-stainless steels, but there are also some High Carbon stainless steels. I’m not trying to correct your use of the terminology, just to share that with you. I’ll use SS for stainless steels and NSS for the non-stainless steels, here in this forum thread.
I used to think the High Carbon NSS were easy to sharpen and sharpened quite well to yield extremely sharp results. As I acquired more chef’s knives made of more different steels I learned that rule didn’t necessarily hold. The only way I learned the characteristics of the different steels was by sharpening each knife.
I learned early on that many of these Japanese Steels, both the SS and NSS will not sharpen, or sharpen well with W.E. diamond stones. That is when I had to begin using Japanese whetstones mounted on W.E. paddles. I have not come across any Japanese Steels I cannot sharpen with the whetstones. They still may not be easy to sharpen, even with the whetstones, but they can be sharpened. Most of them well. My experience was roughly like your, even when trying a relatively fine grit diamond stones, like the W.E. 1000 grit, it left a rough ragged edge, I wouldn’t expect from such a fine grit.
The first place I like to start is to know the steel type and Rockwell hardness. Sounds like that’s a dead end for you. It does help some knowing which steel it is, but it won’t tell you everything. In general SS harder then a steel like VG10 @ HRc 60-61, for example, requires the use of whetstones. But, depending on how the steel is made I’ve found some VG10 steels may be hardened in a way that one makers VG10 is harder, more brittle and chip prone, then another maker using the same VG10 steel. The sharpening characteristics between the same SS used by the two different makers may be day to night. The only way to really determine how well the steel can be sharpened is to try to sharpen it.
I will say it’s easier and quicker to sharpen knives with the W.E. diamond stones then to use the whetstones. The diamond stones are more consistent in thickness and they’re magnetic so it’s easier and quicker to working with your angle cube to make angle and micro-angle adjustments. Whereas the whetstones are non magnetic, a little messy and consumable. They wear done and require lapping/maintenance to keep them flat and true. I use a magnetic stone adapter to facilitate using the angle cube on the whetstones.
Enough of the backround…I knew I would get too involved…
The first two on the left appear to be the typical chef’s style knives called Gyutos. They look to be around 8" or 210mm, I’m guessing.
The first one is made with a black coating that’s intended to inhibits the steel from reacting and also can help with food release from the blade. It does have some blackened or mottled appearing steel, called patina, on the blade path or Kiriba, from when the knife steel reacted with acidic foods.
The second Gyuto with it’s more uniform dull gray color and appearance may be a SS knife, or it may have a SS cladding. That is it’s NSS in the core and the blade’s cutting edge, with layers of softer SS on the outside. The SS cladding is to help with edge durability and to make it easier to maintain.
The fifth knife from the left, the long thin knife is obviously NSS and has reacted to foods causing the mottled black patina. I’m guessing this is a Yanigiba or Sushi knife, (although that knife type are often single beveled knives) or it may be a Sujihiki or Japanese slicing knife. Some Japanese knives are made to emulate the blade shape and characteristics of more traditional Western or European type knives, so it’s hard to tell, for sure. (I can’t see the tip on that long knife but it appears it may be angled or broken off).
The knives can be sharpened well with the W.E. sharpeners, but not with the diamond stones. From your initial post it sounds like you will need to be using whetstones to sharpen them. I enjoy using these Shapton Pro Stones. These are a “splash and go” type of whetstones. You just spritz them with water to use them. I’ve been using these stones and some other type whetstones for many years now with very good results. There are other whetstone types requiring a full soaking in water. How the two types of whetstones are used is slightly different.
It is a pretty expensive initial investment you’ll need to make, to get into whetstones. It’s another different skill set you’ll need to learn, too. The sharpening strokes are the same as the ones we use sharpening with the diamond stones. I linked the seller where I made my most recent purchases, above. There are only a few makers of these whetstone set-ups, out there, that I have come across. Most of these makers are in home or small shops made by guys cutting full size Japanese Whetstones with tile wet saws. Pretty much any brand of whetstones that can be purchased and cut, can be used. As long as you have someone willing to make them or if you can make them yourself. Then they’re mounted to a backing plate then mounted onto original W.E. paddles. Prices vary depending on the grits, finer grits are pricier. A full set can be $1000 to $1500, or more, depending on how complete the stone sets are. Also maintenance lapping plates will be needed. Another initial expense.
I can’t see getting into this discussion any deeper here because IMO the whetstones are the only way to move into sharpening these steels that you can’t sharpen with the W.E. diamond stones. I’m happy to help you further if I can. The discussion can be endless…each Japanese steel I’ve sharpened has it’s own nuisance, but the whetstone sharpening method I’ve learned generally works well for all the steels. Just some are harder and trickier to sharpen then the others.
