S90V Shechita started!

[taz575]

The same customer I did the CPM 20CV Shechita wanted some more in S90V, which is MUCH more wear resistant and harder to grind. I have been putting these off for a while so I could get some shop upgrades done. I had to insulate the shop, get a better dust collection system, and do some grinder upgrades. I needed to get a tilting grinding table so I could slide the blade along the table against the belt instead of using a jig and trying to make a massively wide tool rest to keep the grinds consistent.

I have to make 2, 18" long x 2.5" blade Shechita, 4 Shechita with 5" long x 2" wide blades and 2 with 4"x2" blades. I got 2 bars of S90V and got the 8 blades cut and off to heat treat and got them back this past Fall. Shechita are used for slaughtering animals so they are Kosher. They need to be basically straight razors, highly polished edges, smooth blade finish, wide enough so the back of the blade is outside of the neck, etc. 1 clean slice with no tearing, ripping or pulling to slice the neck of the animal is a pretty hard task! The large ones are for cow, there are medium with around 12" blades for lamb and the smaller ones are for poultry.

I started on them finally! I decided to go with the 5" to start with. I set my table to around 3.5 degrees and started grinding. I spent some time playing with different ceramic belts (VSM Actirox Destroyer, VSM 885, 870, 880, etc). This steel is extremely slow grinding, plus the blade width (2" wide) doesn't help things! I found when the belts get duller, they start polishing the steel and not really cutting it. About an hour into grinding with 36 grit belts, I was around halfway up the blade height wise. Took around another hour to get around 1/4" away from the spine after making the angle a bit less (I think I ended up around 2 degrees!). I can usually grind both sides of a 4" long, 1" wide Magnacut blade with a 36 grit belt in around 10-15 minutes tops. The 60, 80 and 120 belts went OK, and I went to a hard felt platen to get a better finish to them. I went to a 220 grit ceramic belt (fresh belts only) and that did OK, but was my finest ceramic belt grit. I went to some other AO belts that normally leave a really nice finish (Norton Noraz, 3M Trizact Gators and VSM Compact Grain belts) that help remove the coarser scratches and make the blade smoother and they did pretty much nothing except burnish the steel. I went up to a 30 micron grit and then 2K compound on a cork belt and just succeeded in polishing the high spots! If I ran my fingers down the blade, I could steel feel a lot of deeper scratches and the surface felt rough. Pictures show the 3, 5" Shechita at the finest satin belt finish I could get:

Back to the Ceramics and grinding lengthwise on the wheel to remove the older scratches. Got those removed and cleaned up with the 120 and 220 ceramics. Went back to the felt platen and the AO belts to put a nice satin finish on it and nada. The AO belts barely scratched the surface!!! Like they literally just scuffed the surface and didn't really do much to it. I found an old 600 grit SIC belt and that worked a bit, but it's a worn belt and is slow.

Finest satin belt finish on the left, 220 ceramic with a little 600 SIC cleanup on the right. I can feel almost all of those scratches on the blade on the satin belt finish. The 220 grit finish feels smoother than the satin belt finish!

Finally broke down and spent some $$$ on new SIC and Ceramic higher grit belts to try out. I am glad I didn't start with one of the 18" ones first!!!

[Kekoa]

Sounds like you got your work cut out for you! I would be tentative about the thought of grinding something small out of that steel, but "18, who-doggy, that is going to be something. These will be impressive when they are finished. Good luck!

[taz575]

Yeah, it is going to suck! But I got some of the SiC belts in yesterday 220 to 1000 grits, so I gotta see how those do! Gonna suck to sharpen them, too!

[taz575]

Got the 4, 5"x 2" Shechita ground a bit more!

[taz575]

Almost ready for handles on the 5" blade ones! I went to a 16 micron satin belt finish on these so far

I am going to re order steel and grind the 18" x 2.5" ones before heat treating. I have a lot of hours into these 5 to get them to this state after hardening. Belts glaze over and stop cutting and start burnishing the steel, but the same belts cut great on other hardened steels still. Go figure! I am going to try to slice up the 2 hardened 18" x 2.5" blades to use as other type of blades.

[taz575]

So I got one of the 5" models fully done and handled! I spent a bit over 5 hours on the grinder working on this blade yesterday to see how shiny I can get it. It was at a 16 micron belt finish before, but wasn't as polished and there were lots of left over scratches from previous grits. I went back to 120 a few times trying to get some deeper scratches out that don't show up as well until it's more polished. The scratches would really pop out as it got more polished and some were obviously deeper than others, so I would get up to 400 or 600, then go back to 120 and start over again. Lots of trials with different belts, using water or Windex on the belts, etc to get them to cut well. Ceramic and SIC belts still work best, but even those wear out pretty quickly. Windex seemed to help keep the belts cutting.

Reflection is me and the kitchen curtains in the other picture. I will try to get some better pics in natural light before I ship it to the customer to make sure the finish I am getting is good enough. With Shechita, they need to be highly polished, but this steel does not like to be polished, especially after hardening! It holds onto scratches like nothing I have seen and sharp belts stop cutting. I did some regrinding at 120 grit and went at an angle to the belt around 30 degrees so I could make sure I got all of the scratches out from the previous grits. I went back to perpendicular to the belt with 120 grit and spent 10 minutes and still had the 120 grit diagonal scratches I just made showing. Had to go to a newer ceramic 120 belt and spend a lot more time to get them out.

Handle is Black G10 Suretouch. It is rubber and G10 in layers, so it has a really nice grip! Sharpening wasn't as bad as I thought it would be. I used a ceramic 220 grit belt to rough in the bevel, keeping the speed very slow. 320 grit Shapton Glass Stone, Bester 1200, Rika 5K and then stropped on my 16 and 3 micron Diamond strop, then to a 1 micron diamond strop. Edge is crazy sharp and wasn't much harder to sharpen than most of my other stuff! Grinding on the belt sander is another thing!

New steel for the big ones should be delivered today, so I have a bunch of stuff to prep for HT in the next few days. Tuna Poker blades, AEB-L Pizza Cutter wheels finally and the S90V, plus some Nitro-V and maybe some more Magnacut will be in the HT batch.

[Kekoa]

Great work! I find it pretty interesting that it seemed to sharpen as well as it did considering how difficult it was to grind. As a knife user, it sounds like it might be a fun steel to have, but if I was making knives, I would probably stay far away, ha ha!

[taz575]

I got more steel in to grind the 18" blades before HT. I was able to rough grind 2, 18"x 2.5" wide blades in 2 hours when the steel is soft! Going to get them cleaned up for HT this week, but the steel is much easier to work when soft.

I did grind out a smaller 3.25" S90V EDC/bird and trout style blade and the narrower blade wasn't as bad to grind as I thought it would be after hardening! I think the wider blade of the Shechita's is what makes it a pain since it's about a 1.5-2 degree grind angle, so there is a lot of steel to remove on a wide blade. A hunter style blade isn't all that bad to grind! Going to make 9 more of these with different handles once I get the remainder of the hardened steel cut down.

Sharpening isn't too bad with S90V either. I cut the bevel with a 120 ceramic belt going slow, then went to a 320 Shapton Glass Stone, Bester 1200 and Rika 5K. I deburred after the Bester and Rika with my 14 micron diamond strop and then stropped with the 3 micron diamond side of my strop and got a stupidly sick edge that shaves easily and just slips thru receipt paper like it's not there! I was really worried about having to get new stones for the S90V, but that doesn't seem to be the case!

[Kekoa]

I've been reading people talk about S90v and have been getting more and more interested, which is a little weird honestly because I tend toward low alloy high carbon, and don't put a lot of stock in edge retention. I guess I also have done a little looking into Rex45 and K390, so maybe I am finally becoming intrigued by these super steels now that I have been in the hobby for a little while. S90v sounds like something I would like in a neck knife sized blade, but I have to keep my knife obsession in check for now.

I am curious, is there a concern that those "18 Shechita will warp if you grind them before HT?

[taz575]

I am leaving them thick for less warping and people usually use quench plates to keep the blade straight. Warps can be straightened too. One guy who uses s90v takes the edge down to .020" before HT and finishes the blades to 400 grit, so he basically has to remove any scale from heat treat, do the final blade finish and sharpen.

[taz575]

Got the other 3 polished up and handles are roughed out! Almost done with the 5"! Gotta do 2, 4" blade Shechita and the 2, 18" x 2.5" ones are roughed out at 36 grit. Gotta clean them up to prep for heat treating this week coming up!

[taz575]

The 5" are heading to New York in a few minutes!

[taz575]

Quick pics of the 18" x 2.5" wide blades on the 2 big ones! Got them rough ground to 100 today, gotta do some more cleanup and prep for heat treating! I am going to leave the edge thicker so they won't warp as much during heat treat and grind to final thickness post HT I think. They are around 22.5" long tip to the end of the tang.

I'll try to get some comparison pictures, but these are massive! I went with .100" thick barstock on these as well to save some weight and time grinding.

[taz575]

Got the mega ones back from heat treating and did the final grind and polish on them as well as the black SureTouch handles! They just need sharpening! Blades are 18" long, 2.5" wide and around 23" oal. To the left of them in my Tanaka R2 240mm gyuto for a size comparison. These are massive!!!