1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

What grit-level is optimal for CPM S90V?

Discussion in 'Maintenance, Tinkering & Embellishment' started by Morthawt, Oct 8, 2018.

  1. Morthawt

    Morthawt

    60
    May 30, 2017
    As I understand it, S90V needs a toothy edge in order to get the benefits of long lasting edge that the steel is capable of. I have all diamond stones in grits of a credit card sized 350 ish and 600 on the other side, a heavy double sided stone of 600/1000 and a little blue EZE-LAP super fine (1200 grit?) stone but it's really small and practically all plastic handle and a tiny bit of diamond in comparison.

    Then I have a basic leather strop with no compound.

    For a toothy, long lasting, effective edge, what kind of grit should I be using? What would you consider the minimum or maximum grit for a toothy edge for this? What are the pros and cons of choosing a lower grit or the effective maximum grit?
     
  2. Wowbagger

    Wowbagger

    Sep 20, 2015
    8,000 DMT
    I like "em push cuttin' polished even if they have these funny vanadium carbide things.
    Look at it this way it won't be that sharp long, the carbides will be as well formed as possible AND on a micro scopic level it will still be saw like just with finer teeth. I mean the carbides are still finer than those little teeth. :thumbsup:
     
  3. PeterS84

    PeterS84 Sharpening addict, collector of super steels Platinum Member

    183
    May 9, 2018
    I've polished S90V all the way to a 0.025 micron level. That said, I find that for me the optimal level is about 1200 grit or a DMT Extra fine. Push cuts and shaves quite well but still has enough "tooth" to grab/bite into materials common in my EDC cutting tasks. As always, YMMV. I don't think there's one "right answer" to this question -- very much depends on how you use your knives and what your expectation of its performance is like.
     
    Chris "Anagarika" likes this.
  4. Mo2

    Mo2

    Apr 8, 2016
    I have most around 600grit but one around 1500 grit. Though I haven't done any tests to say one is better than the other.

    Cedric Ada had 440 cuts on 600grit diamond edge on Benchmades s90v. Don't think he's done a polished vs coarse edge on s90v yet. But his work sharp edge was much lower # of cuts but not apples to apples. Ie edge angle or brand.

    I'd suggest that 600grit is really all that's needed because going to 1500+takes forever and I'd assume minimal gains would be had if any.
     
    David Martin likes this.
  5. Jason B.

    Jason B. KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Jun 13, 2007
    Regardless of steel the coarser edge will always last longer when abrasive wear is the main factor of edge dulling.

    That said,
    What you are cutting and how you are cutting can play a big part in what edge you should have on the blade. Anywhere between 300 and 1500 is usually good for EDC knives but it's always best to fine tune it to your individual needs.
     
  6. Morthawt

    Morthawt

    60
    May 30, 2017
    Personally, I typically am cutting through paper, card, thick cardboard, tape and gummy adhesive attached to all of the above now and then. Occasionally I may cut a bit of cord but that is rare and also occasionally I may just shave a few errant facial hairs or again on a rarity cut a couple of plastic cableties. But I have more than 1 knife so if one cannot do it all it's not that big of a deal.

    What are the downsides and upsides of sharpening to, say 350 grit final vs the same pros/cons for 1200 grit? I read on the science of sharp that people have had shaving razors at low grit and they were fine, smooth shaves which did not cause any problem. But I do not recall if there were techniques involved in making it a smooth cut or if it was just a statement as-is that 350~ grit is just as fine for shaving as 8000 or something they had as their comparison. I am just trying to figure out what will give me the longest lasting edge which is as broadly as possible useful for as many materials as possible. I don't really want a fringe case where it's great at shaving but is terrible for everything else, or the opposite end of the scale. For EDC I really want broad capability with proper cuts, not messy ripping/tearing "cuts" etc.
     
  7. miso2

    miso2 Gold Member Gold Member

    Nov 19, 2014
    I used to try to get >#2,000 polished edges on my knives.
    Then, I tried #600, #400, #320, and #240 (all silicon carbide stones).
    I now sharpen all my knives at #150 (diamond) and occasionally use 1 micron diamond strop right after #150.

    It works fine for most tasks from cardboard cutting to fruit/vegie cutting, and lasts quite long.
    You can cut soft tissue paper without tearing it.
    You can also shave if you have to.
    I do use my knives to shave my neck area where my shaver doesn't work well.

    I say #600 diamond (DMT red) feels like #400 or #320 silicon carbide and might be a good midway.
     
  8. Morthawt

    Morthawt

    60
    May 30, 2017
    What would you say are the downsides at 150 grit diamond sharpness?
     
  9. David Martin

    David Martin Gold Member Gold Member

    Apr 7, 2008
    I have run several cutting tests on s90v and found it to cut longer when sharpened to 600 grit vs 1200 x fine. The material I was cutting
    during 2 of the tests,-- I was processing chickens. Tender 8-9 week meat birds. I tried to avoid hitting bones as I worked. The difference
    was 3-4 birds less for the x fine. 12-13 at 600 grit. Then I cut strands of Beargrass. This stuff is nasty to handle and cuts your hands. It will cut right
    through a glove. After this test the work gloves were shot. It cut (close to)250 strands. I took each test to a dull blade. In each of these tests it responded like a normal steel. It dulled by curling. The edge gets weak / fatigued through working pressure against it and then it would collapse and to one side. The edge can easily be brought back to a working sharpness by lightly running it down a diamond rod using a
    edge trailing stroke, 1-3. No magic about the steel. DM
     
    Last edited: Oct 11, 2018
  10. miso2

    miso2 Gold Member Gold Member

    Nov 19, 2014
    Not much really, at least for my cutting tasks.
    Edge at #400 may work little better in push cutting, say, envelope paper.
    I would imagine it doesn't fare well in woodworking.

    The real downside is, though not sharpness, burr removal, especially for CPM steels (I own S110V but not S90V).
    I can just finish on the #150 stone for most steels but need to use the strop for CPM most of the time.
     
    J D Wijbenga likes this.
  11. Bob6794

    Bob6794

    Apr 21, 2013
    We all have slightly different cutting tasks and preferences. Only way to be certain you be happy is to experiment. In real world use and not testing you probably can't tell the difference in how long you can go between sharpenings just by changing what you stone you sharpened it on, especially with such a wear resistant steel.
     
    Chris "Anagarika" and miso2 like this.
  12. David Martin

    David Martin Gold Member Gold Member

    Apr 7, 2008
    I may have to take mine to the coarse, 325 grit an see if I like the edge it leaves and how it cuts. DM
     
  13. DeadboxHero

    DeadboxHero Triple B Handmade Knives, Big Brown Bear Knifemaker / Craftsman / Service Provider

    Mar 22, 2014
    Best advice you'll find
     
  14. M-S-T

    M-S-T KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    64
    Sep 20, 2016
    I Agree
     
    DeadboxHero likes this.
  15. Morthawt

    Morthawt

    60
    May 30, 2017
    Good advice. I guess I am trying to finetune my understanding of the grit level and impacts on changes in cutting performance so that I can make a good decision on what grit level I personally want to use. The science of sharp website has me confused because I thought higher grit was needed for shaving yet both that site and people here have said you can shave with relatively low grit sharpening too. So I am just confused a little bit.
     
  16. Eli Chaps

    Eli Chaps

    270
    Apr 20, 2018
    For arm hair if you properly apex the edge you should be able to shave off very low grits. It might feel ragged and maybe won't be the cleanest but it should still take hair off the arm. Facial hair shaving is a lot more sensitive obviously so that kind of shaving is different.

    For me, if I can shave arm hair, then the blade is sharp. From there it is a matter of refining that edge to whatever level I want.
     
    Chris "Anagarika" and Mo2 like this.
  17. Morthawt

    Morthawt

    60
    May 30, 2017
    So am I right that:

    A low grit finish will still cut properly (not tear) but the cut it's self will be less "clean" and fine/smooth.

    A low grit (particularly for supersteels with carbides) will cut longer due to the carbides sticking out more.

    A higher grit will cut more smooth, fine cuts and cause less "trauma" to the surrounding material on a microscopic level while cutting.

    A higher grit will cut on a mere push where low grit might not.

    One analogy I just thought of is my Gerber multitool has a tungsten carbide jigsaw blade on it. Thick chunky bits of carbide all over it, visibly large. I can run it across my hand and it does not cut me at all, yet when I run it against hardened steel padlock shackles it will ultimately cut through them in 5 minutes of sawing/cutting. Does this mean a lower grit knife finish is worse on softer materials and a higher grit would work much better on soft materials?
     
  18. DeadboxHero

    DeadboxHero Triple B Handmade Knives, Big Brown Bear Knifemaker / Craftsman / Service Provider

    Mar 22, 2014
    All depends,
    there is no universal "best" edge finish.

    To say polished is better then toothy and vice versa is a complete misunderstanding of how to use edge finishes.

    Shaving your face with a razor is at one end of the the spectrum and NEEDS polish so the blade can slide over your skin without irritation and cleanly "cleve" off the hair without any drawing of the edge. Just a straight push with minimal force and a clean cut.

    At the complete other end of the spectrum is draw cutting thick natural and synthetic rope, you don't want polish, it slips on the rope, you want teeth on the edge that "catch" the fibers and shred them apart with the lightest draw of the edge across the rope.


    In reality, we aren't shaving our faces with our pocket knives nor is the AVERAGE person cutting insane amounts of rope everyday.

    So we play with different combinations of "polished toothy" edges.

    An edge that still has teeth that aren't completely smoothed out and has some "bite" and endurance yet still has the push cutting, the finesse and precision of a polished edge.

    It is a compromise of the two spectrums.

    Like Jason said play with the 300-1500grit range. Also, you'll get different effects from different stones in the same grit due to bonding vs coated abrasive so play with that.

    Lastly, you can add diamond and CBN stropping to really fine tune the finish you like.
     
  19. Morthawt

    Morthawt

    60
    May 30, 2017
    The stropping with compounds is one thing I have not experimented with. At present I have a cheapo strop. I wouldn't want to go crazy though and have a million strops all different grades. If I were to use some form of compound on a strop I would want it to be generally useful to help de-bur an edge quicker rather than specifically trying to get a super polished edge. Given that, what kind of compound micron rating would you say would suit me to literally just aid in de-burring, regardless of what grade sharpening the knife has?
     
  20. DeadboxHero

    DeadboxHero Triple B Handmade Knives, Big Brown Bear Knifemaker / Craftsman / Service Provider

    Mar 22, 2014
    Just start with 1um diamond spray on leather and go from there.
    Also you should be deburring on the stone then removing the wire edge (frayed base of the burr) on the strop.
    Any Burr should be created as small as possible.

    If you jump to a strop without any deburring work, most of the time you'll just be raking the surface of the leather with a burr and just straightening the burr out making a foil edge.
     
    Chris "Anagarika" likes this.

Share This Page