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These knife sharpening stones combine the sharp cutting action of diamond with a very wear resistant resin bond. While they don’t cut quite as fast as a plated bond they will leave a much finer scratch pattern for the same grit. When the cutting action degrades they are easily dressed with loose abrasive on a flat surface with a little water. The 1×4 stones only take about 10 seconds to make them work like new again. The diamond/resin matrix is 1/16 inch thick or 1.5mm. While this may sound thin with proper care they should last a lifetime for most of us. They are softer stones so you can carve into the finer ones if you’re not careful, the bigger diamonds in the coarser stones keep this from happening. They need to be kept wet during use, if you let them dry out while sharpening they will glaze quickly which may require dressing to fix. For general cleaning just scrub them with your fingers while wet after using, rinse, and let dry. While this does leave some color on the stones it doesn’t affect their performance. A deeper clean is best done with a paper towel and rubbing alcohol or Bar Keepers Friend, Comet, and Ajax all work well too. Any other solvents should be avoided as some can attack the resin and alkaline cleaners, like Simple Green, will attack the aluminum backs.
The information below is based on my own observations and preferences. We all like to sharpen differently and I am sure not everyone will agree with what I suggest so let’s just call it a good starting point.
The grit rating is in microns –
I chose this as it is the most logical size rating and is the easiest to compare with other sizes since it is the measured diameter of the abrasive. An 80 micron stone uses abrasive that is half the diameter of a 160 micron stone, same as 5m to 10m.
What knives work with these knife sharpening diamond stones –
I don’t like to use these stones on softer steels. Anything less than about HRC 53 and diamond seems to smear the steel around more than cut it leaving a less than desirable finish. The harder the better, diamond likes to fracture and not plough through. They cut Maxamet nearly as fast as Henckles knives and they cut ceramic just fine too.
They need to be dressed before using –
Generally the stones are shipped as molded and need to be dressed before using them, for several reasons. Proper dressing is very important with these stones and your going to have to learn how to do it so it might as well be from the start.
The break in after dressing-
After dressing these stones are extra aggressive and can/will lose some abrasive on the first knife so expect it. I am overstating it somewhat but this is when you can get stray scratches, don’t use your favourite knife. They will be extra sharp with more feedback but leave a coarser scratch pattern with deeper scratches on the first knife or so. After that they settle down and should work the same for many sharpenings. This settling down is not loading up, and it is good. They will cut a little slower but leave a much better scratch pattern with shallower scratches. These stones tend to leave a finer scratch pattern than the phenolic bond diamond stones that I have sharpened with.
How much pressure should you use –
With these knife sharpening stones you need to use less pressure when sharpening. The lighter the pressure used the shallower the scratches they will make and the longer the stones will go between dressings, but they do like some pressure. The best way to learn it is to start very light and slowly increase your pressure when you first start using the stones. The more pressure you use the better they will cut but you will reach a point where they degrade in performance quickly. When this happens give the stone a quick dress and now you have a better idea of what too much pressure is. The stones should be dressed 2 or 3 times when new to fully break in and it seems to work better if you use them between dressings so go ahead and use too much pressure a few times, these are new stones, learn their limits. Dressing only removes .0001″-ish of resin on the finer grit stones when done right so your not going to wear your stones with a few extra dressings and you will learn a lot about them. I think the happy zone is about half way between no pressure and too much pressure. They still cut quite well and will go a long time between dressings.
Edge leading or edge trailing passes –
I like to use edge trailing passes once I reach the apex, but use both to get there. I find that edge trailing passes leave a keener apex and that there is less stress on it. I also think the stones go longer between dressings. This should at least be food for thought.
Grit progression –
There are no extra grits between the coarsest and finest. The 160m is good for coarse work or reprofiling but I start with it with very dull blades. The 80m is a very good stone to start with for a dull knife but is too fine for doing much work, it will take forever reprofiling but is capable if you have the patience. The 40m is the first stone I try refining the apex with, the coarser stones simply can’t do it. Unless you are after a very coarse edge I would suggest the 40m being the coarsest you finish with. It is the first to really refine the edge but leaves it pretty toothy. The 20m is really refining the apex nicely but with a fine toothy edge. The 10m leaves a hazy polish with no tooth. The 5m leaves nearly a mirror polish, especially on the harder steels.
I don’t worry about removing burrs until I am done with the stones, at which time I switch to a strop. So far I like bare leather for anything short of the “super” steels, which I use 1 to 5 micron diamond with a water carrier to load the strop. I find that cream or oil based carriers cause the leather to create more drag on the knife while stropping and cause more noticeable, under the microscope, convexing of the apex.
5 micron is the finest diamond that works with this bond. I have tried 4, 2.5, and 1.5 micron diamond with this bond but they don’t really work, it seems the bond is too hard for this fine of abrasive. 4 micron works on extremely hard steel, like Maxamet, and both the 4 and 2.5 micron diamond work fine on ceramic, but the difference compared to the 5m stone is minimal so not worth buying. To go any finer I believe a softer bond is needed, like balsa or bass woods, or leather. I know this is now called stroping but loaded with diamond it still cuts pretty aggressively.
How many passes per grit –
I am a guided sharpener devotee so this information is based on my experience using a guided sharpener with 1×6 inch stones. Once I am done with the first stone then I use 10 edge trailing strokes per 3″ of knife blade length per side with a 1/16″ish wide bevel. I have tested this extensively inspecting with a microscope and if done well there is no difference between 10 and 200 strokes per grit when you are done.
This is the big one. How these stones are dressed will have a huge effect on how well they perform. The only way I dress them is with loose abrasive on a flat plate with enough water that the abrasive doesn’t clump up or run away. All you want to do is wear away some of the resin to better expose the diamonds, which when done right does not change the thickness of the stone. I think the best way to show how to dress these stones is to do a few in a video.
How often you dress depends on many things but I sharpen over 40 knives with my finest stones between dressings and never dress the 80 or 160 stones. If you keep them wet while being used, use light pressure, and clean them when you are done they are very stable, slow wearing stones.
The abrasives I use to dress the different stones:
160m – 24 grit
80m – 60 grit
40m – 60 grit but fresh 240 grit works too
20m through 5m – 240 grit