Sorry for the long post in advance, but I wanted to chime in here to give some info on working with S90V since I got baptized in it recently and I want others to learn from my mistakes! I got it hardened to 61 HRC and then ground 4 blades from it post HT. 1/8" stock, blades were 5" x 2" rectangles, full flat grind, for Kosher Shechita/Chalef knives. About 25-30 hours later, I had 4 shiny blades, stupid thin at the edge and wickedly sharp. It was a ROYAL PITA. Even with VFD, ceramic belts, etc, it was a nightmare for a wider kitchen knife style blade!! I ran around a 1.5-2 degree angle for the blade grind itself on these, they are 1/8" thick stock. Thats a lot of metal to remove on a wide surface area, which means less pressure on the belt since it's over a wider area. Grind smaller sections and work your angle back towards the spine for better results on wider blades.
I used a variety of Ceramic belts. Sharp fresh belts are a must and when the belt starts burnishing the steel, stop and get a new belt. The belts typically have a lot of life left for other steels when they start burnishing, but not for S90V! It's bad when I saw my fingers in a very clear reflection at 60-120 grit belts!! I found a mid level speed and more pressure cut better and I tried to run the belts wet, too. I ran the blades on the wheel like a surface grinder to make sure I got all of the coarser belt scratches out at 120 and again at 220 grit and that made life a bit easier. I used VSM ceramics 880y, 885y 36, 60, 80 and 120 and Actirox 36. Hermes flexible Ceramics in 120 and 220. Norax Ceramics in A65, 45, 30 and 16. Trizact Ceramics in A45 and A30. SIC belts 220-1000, I ran these slow and wet with a good bit of pressure and then cranked up the speed, which helped burnish and polish the steel at the finer grits, running wet belts. The blades still had left over scratches, so they were not a perfect satin belt finish, but the guy loved them. They were smooth and you didn't feel the leftover deeper scratches. Key take aways: if they burnish, save that belt for other steels and grab a fresh one. Mid level speeds and pressure are good, keep the belt/blades wet!
AO belts, even Compact Grain belts, J Flex AO Supernova and Klingspor belts, etc, barely scuffed the surface when I tried them. Ceramics are key with the steel hardened and SiC do OK, but don't last long. I used soft platen (leather and felt) and found that the scratches come out better on a glass platen than a soft platen. The big ones will be full flat grind and the Ceramic Noraz and Trizact are thicker belts and do better on the glass platen than the thin SiC belts do.
I used a 120 grit ceramic VSM belt to cut the edge bevel, which was almost a zero edge, maybe .05-.010" or so?. Then I used a Shapton GlassStone 320, Bester 1200 and Rika 5K and used diamond strops at 14 micron (deburring and after the Bester 1200), 3 micron and 1 micron diamond after the Rika 5K and got a very crisp, sharp, smooth aggressive edge. I was shocked at how well those stones did on the steel and how quickly they worked! Once a bevel was roughed in, sharpening was not bad at all! I was truly shocked at this! I thought I would need to buy diamond stones, but the water stones got a sticky sharp edge and the diamond compound on the strops refined it even further!
I looked at the 2 hardened blanks that were for the 18" x 2.5" wide blades and said hell no! One of those blades has roughly the same surface area of the 4 narrower ones I did above!!!
Ordered more steel and am grinding the big ones pre HT this time! Much easier! 2-3 hours to get both of them to a nice 100 grit belt finish so far, but I still have more grinding to go! And a FYI, 24" x 2.5" x 3/32" thick steel bar is around $80. Not much more than Magnacut or other CPM steels, which are around $110 for a 36" x 2" x 3/32" bar. Grinding pre HT isn't all that bad, but the steel will still burnish on you, so I have been keeping the speeds slower and letting the belt cut the steel. Hard platens work better than the soft platens do.
I cut up one of the big, hardened blanks using an angle grinder slow and keeping the heat down and putting the cut edges at the spine and made a 3 1/8" bird and trout blade for myself to test the steel out. Sharpening was pretty easy, .010" at the edge, same 120 belt, stones and strop progression and I got the same, nice sticky sharp crispy feeling edge. Cleaned about 150+ trout a couple weekends later at a Take a Vet Fishing Derby (and a couple bass), most removing the heads and gutting them, including the small bass. I had one small wrinkle that matched the spine of one of the larger bass. I used the 14/3 micron diamond strop and got most of the wrinkle out in a couple minutes. Edge retention was excellent! A buddy was using an AEB-L blade 62 hrc that was thinner behind the edge and that one had a little micro chipping to it in 3 places. I thought the S90V was going to chip out a lot more and was pleasantly surprised! I gotta slice down the other blank into useable smaller pieces. In a 1.25" wide blade, the steel wasn't all that bad to grind even post HT and I got a nice satin finish I am happy with for a Bird and Trout knife. The Shechita/Chalef knives need a much more polished, smoother finish, which is a painful and time consuming process!
So if people want a kitchen knife in S90V, the toughness should be plenty and similar to other steels. Grind soft (pre HT) and get fresh ceramic belts!! I know some guys that take it to .015 at the edge and to 400 grit pre HT and then do a convex edge. Sharpening a thin blade is not bad at all, even with regular stones. Chip removal or thinning, you will want diamonds or a coarse ceramic belt on a belt sander and work up for the grunt work, but with the edge holding of the steel, thinning won't be much of an issue unless you need to remove a big chip.
I did another large Shechita in CPM20CV a while back and the S90V was noticeably harder to grind post HT (about twice to 2.5 times as long for the same surface area,) but the sharpening seemed a bit easier for some reason?
Hope this gives some info to helps others out! I just saw the Supporting craftsman membership option, so I just purchased it right after making the post, so hopefully that makes it ok! I enjoy making and using kitchen knives in my spare time, so now I can do some more stuff on the forums!
