While this is not a comprehensive review, hopefully my initial observations about these stones will still be helpful for some. The stones that I have been trying out are the Sigma Power Select II stones in 1K, 3K, 6K, and 10K grit (JIS). Also in the progression is the Sigma Power 3F Carbon #700 and the Sigma Power Ceramic 13K. These stones were cut and mounted for use with the Edge Pro sharpening system. They were tested for use on knives, not tools. The knives I tested were all about 60 HRC of various stainless steels. All of the stones, aside from the 13K ceramic, were designed to sharpen high speed steel. So they will cut just about anything you can throw at them. The Select II stones are all pure sintered abrasive. That is to say that there is little to no binder, ceramic or otherwise, in the stone. The stones are all heated and pressurized into a brick of pure SiC, like the 1K, or nearly pure Aluminum Oxide (AO), like the 3K, 6K, and 10K. The 13K ceramic stone is just that, extremely fine blend of AO and natural stone silicates with a ceramic binder.
Sigma Power 3F Carbon #700: This stone is so large that when cut for the Edge Pro, the stone measures 2″ wide. The double width is really great for reprofiling a blade. It helps to minimize the amount of hollow areas that can develop along a blade edge. I love this stone. It’s my favorite of the coarser Sigma Power stones that I’ve tried. (Full disclosure – I personally favor the speed and quality of edge that a silicon carbide (SiC) based stone gives up to about 3000 JIS.) This stone will grind a new edge bevel on a large kitchen knife that has no bevel in less than two minutes – easy. To top it off it stays visibly flat after doing so. Did I mention that I love this stone? Removing and repairing chips in a blade edge calls for a coarser stone, but the 3F Carbon could still pull it off. Unlike the Select II stones, this stone is not pure sintered abrasive. There is just enough ceramic binder in it to keep it’s flatness and not slow it’s cutting ability. In all honesty, I wish there was a 1K and 3K stone made in the same way this one is. However, the Boride CS-HD 400-800 grit (FEPA) are the only stones that I’ve tried that come close to this level of performance in that range. 3F Carbon #700, where have you been all my life?
1000 Sigma Power Select II: After coming off the last review, I’d expect to be disappointed… and I’d be right. The width is nice, 1/4″ wider than a standard Edge Pro stone. The 1K Select II is the only pure SiC sintered abrasive that I’ve ever tried. It proved to be much too friable. I can see why it would work well for wide straight bevels like chisels and plane blades. With these tools you can justify the loss of abrasive for the amount of time it saves sharpening. But it didn’t do well for knives. The stone cuts quickly. However, it looses flatness at an alarming rate when working on a knife tip or heel. It gouges too easily. After rebeveling a knife with the 3F Carbon, the 1K Select II still sustained visible gouging and wear just to remove the scratches from the previous stone. On one particular knife with a curved tip, I felt the need to flatten the stone twice on a diamond plate before finishing the edge. Don’t get me wrong. This stone is not Norton 220 terrible, but it’s not good, in my estimation, for knives. I recommend skipping this stone altogether, going from the 3F Carbon to the 3K Select II stone.
3000 Sigma Power Select II: This is a great kid who might feel bad because he’s not as awesome as his older brother, the 3F Carbon. I wish the stone were SiC but it’s AO instead. However, the AO making up the stone sinters amazingly well. It cuts amazingly well too. If I wasn’t wanting SiC so badly at this grit level, I would say that this is my favorite 3K stone. The stone is fast. Beautifully fast. It holds together well on curved edge bevels too, something a sintered SiC stone couldn’t do. While the 3K Select II can be gouged and does release abrasive quicker than some other stones, the speed of sharpening makes it worth it. I suspect, but can’t verify, that the sintered AO stones at the higher grit levels cut quicker and release close to the same amount of abrasive through the sharpening process that ceramic Sigma Power, Shapton, and Chosera stones would. This stone can be gouged, but not gouged as easily as say a Naniwa Superstone or the 1K Select II. Overall, I really enjoy using the 3K Select II and it is now my favorite 3K AO based stone. Yep, I like it better than the Shaptons for knives.
6000 and 10000 Sigma Power Select II: This is where the Select II series shines the brightest. There aren’t many stones available in these upper grit ranges and most of the ones that are available are slow to cut. The Select II stones are designed to cut, not polish. But they will begin to polish somewhat if only due to the way AO cuts steel and the decreasing size of the abrasive through stone progression. Basically, don’t expect too much shine from these stones. Again, like the 3K, these stones are fast. I wouldn’t trade them for anything. In fact, I’d dare to say they are the fastest I’ve ever used in this grit range. Ever.
13000 Sigma Power Tamago-iro Ceramic: This stone hails from the main line of Sigma Power stones. The Select II series doesn’t have a stone this fine. I wasn’t expecting much when I tried the 13K. I have Shapton glass stones up to 30K (different grit standard here) and have SuperStones up to 12K. I have to say that my initial impression is that the Sigma Power 13K leaves a mirror finish that is, to the naked eye, on par with the Shapton 30K and it puts the SuperStone 12K to absolute shame in terms of cutting speed. I need microscope comparisons to check scratch patterns between the Shapton and Tamago-iro. The Tamago-iro has a more organic cut to it than the Shapton, but, dang, they finish pretty. With the price point of the Shapton being astronomically high, I can’t be anything but impressed with the Sigma power. First, it was fast. I couldn’t believe how much metal was floating on the stone after just a couple passes. The 12K SuperStone is not even in the same league with the Sigma. Finally, the finish it left was a perfect mirror. The perfect mirror was left by cutting and not just glazing over the tops of the edges scratch pattern. More on this later, but for now, the Sigma Power 13000 is now my favorite finishing stone.