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How Long Does Shaving Sharp Last?

Discussion in 'Shop Talk - BladeSmith Questions and Answers' started by scott kozub, Aug 6, 2019.

  1. scott kozub

    scott kozub Gold Member Gold Member

    291
    Jan 1, 2018
    I've been making knives from AEB-L for a couple years now around 62 HRC on my AMES tester. I think my sharpening technique is improving as is my grinding. I try to get to about .003" BTE before sharpening. Almost sharp before sharpening.

    I'll typically sharpen from 4000 to 8000 on water stones and strop on leather with green compound. I'll take them to an edge that cleanly shaves hair and slices paper towels in either direction. I like to use the knives without stropping between uses to see how long the edge lasts this way. I figure this is what most of my customers will do so I want to judge the performance on that. To me, it seems that I see a noticeable decline in sharpness after only a few uses including chopping up garlic and parsley so a lot of impacts on the board. They'll still shave but not cleanly. After maybe 2 weeks they wont shave anymore or touch a paper towel. They will slice paper cleanly for quite a long time. They will still cut almost anything extremely well but will start to slide on tomato skin which really bothers me. At this point, a couple light passes on a Miyabi hone or back on the stones will bring the edge right back. The strop doesn't help much at this stage because the edge is too far gone.

    I know there's a lot of variables here (cutting board, technique, amount of cutting, whats being cut etc.) but without maintenance, I'm curious how long you would expect a knife to remain shaving or hair popping sharp in the kitchen?

    My reason for asking is that I don't necessarily want to supply a customer with the sharpest knife possible. I want to supply something that will retain an edge that can cut skinned vegetables as long as possible without maintenance. I'm considering running my knives a bit harder or leaving a bit of a toothier edge to see how that performs. I also want to do some edge retention testing but just haven't had the time.
     
  2. DeadboxHero

    DeadboxHero

    Mar 22, 2014
    Polished never seems to last.
    Higher hardness does help but high polish will always have limitations, any deformation of the sub micron shape of the apex and the edge is gone. Having some teeth will still allow the edge to cut despite the subtile Deformation to the radius.

    Dropping the angles of the edge will also help but again it will not make a polished edge out last a toothier one.

    I'm not saying the solution is to make "saw blade" toothy edges but to find a balance between them.

    I'd recommend bumping to 63-64rc to support a 10-12dps angle and a throw on a crisp 1k stone edge that can cleanly push cut paper but still will have the teeth to grip tomato and pepper skin with a light draw of the edge.
     
    Last edited: Aug 6, 2019
    J D Wijbenga, Ken H> and milkbaby like this.
  3. milkbaby

    milkbaby

    579
    Aug 1, 2016
    A lot of kitchen knife knerds will echo what DH said above. Stopping at a 1k waterstone supposedly leaves scratch pattern and edge that will remain toothy which allows slicing stuff like tomato skins for longer even when the edge has degraded whereas a more polished edge won't have that advantage. The problem is supposed to be more magnified with stainless steels with larger carbide volume (and size of carbides) due to carbide tear-out.

    For a kitchen knife, I really don't care if the knife is shaving sharp as long as it works well on the food it's supposed to be cutting.

    How sharp is it off the 4000 and 8000 grit waterstones? Do you need the strop with compound to get it having sharp? You should be able to get shaving sharp off a 1000 grit waterstone.
     
  4. scott kozub

    scott kozub Gold Member Gold Member

    291
    Jan 1, 2018
    These replies are great guys. I need to strop off a 1000 stone to loose the burr to shave have but 4000 and 8000 do shave right off the stone. The strop simply makes it a bit cleaner.

    I'll give a 1000 grit strop finish and try it out.

     
    Last edited: Aug 6, 2019
  5. DevinT

    DevinT KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Jan 29, 2010
    Most makers over sharpen.

    Hoss
     
  6. scott kozub

    scott kozub Gold Member Gold Member

    291
    Jan 1, 2018
    I grabbed a couple knives and took them back to 1000 grit. I got them cutting hair, kind of pulling before stropping. Very light passes before the strop. I had a mushy tomato we just through out for a test and it nearly push cut it. The 3 finger test was also very delicate. I'll see how long it lasts but so far I like it.

    Thanks guys.
     
    DevinT and DeadboxHero like this.
  7. Alex Topfer

    Alex Topfer

    148
    May 1, 2019
    I've always wondered how the person's hair affects 'shaving sharp'. I see dudes shaving the bear skin rugs on their forearms, and then compare that to my wispy, can barely see without a microscope stuff. It seems thicker coarser hair would be easier to cut?
     
    R.C.Reichert likes this.
  8. milkbaby

    milkbaby

    579
    Aug 1, 2016
    Check out this good video tutorial about burr reduction and removal when sharpening on waterstones. Jon studied as a knife sharpener in Japan, and I find his videos very well explained. I do the burr reduction by lowering pressure on the same stone then a variation of the lateral stroke he starts talking about around 6 minutes into the video (I do slightly more edge leading rather than simply lateral stroke).

     
  9. Stromberg Knives

    Stromberg Knives KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    741
    Jan 3, 2015
    I used to over-sharpen my knives. I've tried to find a nice allround edge for my kitchen knives. After a lot of testing I've found that my knives have a sweet spot at 15 DPS sharpened with a Chosera 400 stone and then strop on leather. Toothy yet slicey.

    My regular users get sharpened on a belt grinder with 220 grit, slow and wet. Then stropped on leather.

    I measure my sharpness with a Bess device. I've settled at around 150 Bess.

    Here's some information on the subject.

    https://knifesteelnerds.com/2018/08/06/sharpness-vs-cutting-ability/

     
    Storm W likes this.
  10. Horsewright

    Horsewright KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Oct 4, 2011
    I too was an over sharpener. I was into water stones before they were cool. Use to take everything (personal knives) up to 10 grand. But in real life they cut "funny" as the cowboss would say when I'd toss him my knife as he was castrating a calf and his knife had dulled. After years of experimenting I pretty much follow Stromberg's recommendations. 220 grit (silicone carbide belt) wet and slow but I knock the burr off with a pass or two on the buffer with green scratch remover. Works. Cuts stuff in real life and cuts and cuts and cuts. Had a guy order a knife yesterday. He'd been at a branding and had been assigned by the boss to ear mark the calves. He borrowed a knife (one of mine) from a buddy that was assigned to the roping crew. After 150 calves it was still sharp and he never stopped to touch it up. He ordered his own next day.
     
  11. Storm W

    Storm W

    267
    Feb 19, 2019
    My personal theory is that over sharpening fatigues the edge. I'm blown away by how well a course diamond stone will shave as well as cut.
     
    Natlek likes this.
  12. Cushing H.

    Cushing H. Gold Member Gold Member

    441
    Jun 3, 2019
    I said this before on another thread, but as it reinforces the “over sharpening) points made ... will repeat here. I am one of mlkbaby’s (where did your name come from???) kitchen knife nerds :). . After watching and seeing a lot of japanese cutting techniques, a few things strike me. First, they ate far more careful and sophisticated at food prep than the western tradition (and so i trust them more). Second, and this is the pertinent part, they prefer to SLICE, not cut or “chop”. Long, slow, pulls of the knife across whatever is being cut. Ive tried to practice this for a while, and a few things have struck me: you can cut things more easily and cleanly, it helps the blade edge last longer, and you do not need “razor sharp” (ie the “shaving” test just does not even apply, as the motion of use is just totally different - the micro-serrations from the 220 grit do help for “slicing” motions). Nowadays i use the 400 grit wetted stone on the Tormek system (followed by stropping) ... but i think this would be totally equivalent to the wetted, slow, grinder.

    Horsewright - your users, i doubt, would have the luxury of that usage pattern ... so i guess you get your benefit from a steeper angle and micro serrations? I am making a skinner for a hunting friend of mine, and my plan is to go with 20dps on that one, and sharpen with 220-400 grit.

    FWIW...
     
  13. Taqtaq

    Taqtaq Gold Member Gold Member

    45
    Jun 10, 2018
    I’ll sharpen 440c when with 400 grit and strop on the buffer. The blade will shave for awhile but more importantly, I can probably do 20 caribou before needing a to be just touched with the grinder again.

    Aeb-l I’ll get to x5 (3000 grit?) and buff. I can probably do 10-12 caribou before stropping and doing 10-12 more. I’m not sure when I’ll need to bring it to the grinder yet
     
  14. butcher_block

    butcher_block KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Dec 6, 2004
    i ll be that guy. stop with the "shaving sharp" you really dont know what that is till you hone a straight razor properly. most makers call shaving sharp scraping hair off your arm or leg. a razor that is properly honed will cut hairs without touching the skin (tree topping sharp) ok rant over

    keep it simple most of my kitchen knives get sharpened to 1200 grit DMT hone in house the edge i send them out with is 3 micron film belt run slow and wet with a strop on a bench to finish thats for XHP at 62-63 Rc single bevel kitchen knives and straight razors are the only blades that get the water stone treatment and most the time i stop in the 8K 12K grit range depending on blade
     
    Gary W. Graley and Storm W like this.
  15. Horsewright

    Horsewright KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Oct 4, 2011
    Probably. i guess but they work I know:

    [​IMG]

    And ya sure see a bunch of em around cow country:

    [​IMG]

    [​IMG]
     
    Jason Volkert likes this.
  16. Ken H>

    Ken H>

    Dec 31, 2011
    Guilty!!!
     
  17. allenkey

    allenkey Gold Member Gold Member

    103
    May 19, 2018
    If I am understanding what you are saying right ..i.going against what I've thought for a while... So, you mean more acute edges last longer?

    So a 12dps edge should out last a 20dps edge?

    Also, for you guys saying you are guilty of oversharpening - are you strictly referring to what finish you take the edge to?

    I'm a newbie lol
     
  18. Drew Riley

    Drew Riley

    Oct 17, 2007
    I used to take my edges to a high polish. They'd shave hair, plane wood, shave paper and push cut just about anything.... for about 5 minutes. Once that edge starts to go though, you can barely saw through a piece of nylon rope or thick cardboard. God forbid you tried to cut plastic zip tie. :D I didn't much care for that.
    Anymore, I'll just hit my edges with a 220 to 400 grit belt, and knock the burr off with couple of buffer passes. Sharpening angle will be 15 per side more often than not.
    For my daily user, I'll hit the edge on the buffer every few weeks if I think about it while I'm in the shop, but normally I'll just line the edge back up on a 600g Norton India stone that I keep in my locker at work.
     
    Ken H> likes this.
  19. DeadboxHero

    DeadboxHero

    Mar 22, 2014
    Yes, a more acute apex has a smaller radius, when the point deforms the radius is still somewhat small hence why in cutting tests the lower edge angle is the most significant factor for cutting ability and pure cutting endurance.

    All the factors are intertwined for instance if the steel is too soft it doesn't support the lower edge angles well and will deform and roll in use. That's when I make a knife designed to "cut" I never go under 60rc.
     
  20. Lapedog

    Lapedog Gold Member Gold Member

    Dec 7, 2016
    It does totally depend on the hair. I have the same thing where my knife won’t shave or whittle my hair well but will do so on other people’s.

    Whittling hair is supposedly easier if you go tip to root direction.
     
    mb> likes this.

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