I’ve been thinking about getting a coarser water stone (or diamond plate) for a while, to make shorter work of thinning and sharpening damaged blades. The other (full size) stones I have are the #1000 and #5000 Naniwa chosera and a #13k Sigma Power that I bought last year. The one I use the most is the 1k chosera.
The reason I went for Sigma Power is that I wanted something fast cutting, but less delicate than the chosera stones. The chosera stones are great, but they’re kind of picky about how much water you use, how fast they dry, temperature changes, etc. No matter how careful I’ve been, they’ve developed many small and a few deeper cracks that make me kind of nervous. I had read about people testing Sigmas by putting them in the freezer and defrosting them without any problems. I don’t feel worried at all using the Sigmas. I looked at other stones as well, like Imanishi/Bester, but they seemed to have the same drawbacks as the choseras and pretty much no advantages.
I ruled out diamond plates since I’ve gotten this idea that I won’t enjoy sharpening on them. I like the feel of water stones.
Both the #400 and #13000 Sigma stones are a part of the Select II series, but from what I understand they don’t really belong there, since they’re different kinds of stones. The ”real” Select II stones are sintered without binder, but the #400 has a binder and the 13k is from their old ceramic series and is a mix of natural and synthetic abrasive if I recall correctly. The #400 was developed to be more dish resistant (not hollow out so quickly), but still cut fast.
I got the #400 stone today and tried it out right away. It’s a splash-n-go stone, so I didn’t soak it. I started by thinning a kitchen knife that came hollow ground, that I’m working towards making sabre ground. The new stone didn’t seem to cut as fast as I had hoped. At least there wasn’t as much black (metal) swarf on the stone as I’m used to from the choseras. The finish was kind of rough, but about what I expected. The feedback from the stone is very different from the smooth chosera, but it’s a coarser stone so I can’t really compare them. They feel very different, though.
One drawback I noticed pretty soon was that the loose abrasive in the slurry really scratched up the part of the blade that wasn’t (supposed to be) in contact with the stone. It’s not like I didn’t keep the angle and “painted outside the line”, but I got some blotches on the side of the blade even though I rinsed it thoroughly between switching sides. Another is that it dished quicker than I expected. Again, I’m comparing to the 1k chosera stone, so this could very well be normal/good for a 400 stone.
Then I ground a primary edge on a knife (two actually, the one I had thinned and a small convex paring knife) and: Wow! Now I could notice how fast the stone was cutting the metal away. I took a few strokes on the stone and then checked the edge and I already had a huge burr along the entire edge. The edges were in pretty good shape to begin with, but the difference from the 1k stone was apparent. It was super easy to put the edge on there and after deburring (I use the method where you fold the wire edge over and cut it with an edge-leading stroke a couple of times) the knife cut very well. A very sharp and aggressive edge, but not as rough as I had expected. I stropped it a little with BRKT white compound and called it a day .
Here you can see the 400 edge compared to a 13k edge (straight off the stone, not stropped) I made yesterday. It’s kind of hard to make out where the primary edge starts on the 400 in the microscopic shot, since I thinned the blade with the same stone, but you get the idea from the cellphone photo. Obviously the 400 edge is less even and has a rougher finish, but it cuts very well. I haven’t really mastered the 13k stone yet, so you could definitely get better results than this, but you get an idea of the difference in refinement. At ~220x magnification the edge from the 400 grit stone almost looks chipped.
These are just my initial impressions, but so far I’m happy with my new stone. The biggest issue is the aggressive slurry that messes up the finish on your blade (and your sink) when thinning. It shouldn’t be a problem when doing just the primary edge, unless you use a very low angle. The advantages are the speed and worry-free use.