Thinning - how high up do you go?

Discussion in 'Sharpening Station' started by PappaG, Mar 18, 2019.

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How much behind the edge do you thin

  1. Just behind the edge

    1 vote(s)
    8.3%
  2. 1/3 behind the edge

    9 vote(s)
    75.0%
  3. 1/2 behind the edge

    2 vote(s)
    16.7%
  1. Mar 18, 2019 #1

    PappaG

    PappaG

    PappaG

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    I was reading the "coarse stone" thread and reading about removing scratch patterns.

    I never know what people mean. Do they mean the edge? Do they mean right behind the edge? Do they mean far up the edge?

    I'm not good at starting polls, but my question is two fold - when you thin how far up the blade do you "generally go" (I'm sure its different for different knives but humor me) and second question - when you say you remove scratch patterns with your stone progression, what exactly do you mean? the edge? All the way up the blade road? As part of the thinning process?

    Sorry in advance if my questions suck...
     
  2. Mar 18, 2019 #2

    stringer

    stringer

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    I'll save you some time. You are going to get about 200 responses and they will all be some variant of: It depends.
     
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  3. Mar 18, 2019 #3

    stringer

    stringer

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    It depends on:
    The condition of the knife.
    The intended design and purpose of the knife
    How you want to use the knife
    Your skill and available tools
    Etc
     
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  4. Mar 18, 2019 #4

    geoff_nocon

    geoff_nocon

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    i lay mine flat on the stone. similar to sharpening a wide bevel
     
  5. Mar 18, 2019 #5

    RDalman

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    Thinning-how far-until you're happy (with how it cuts/looks)
     
  6. Mar 18, 2019 #6

    Wdestate

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    Jon from JKI has great videos on YouTube with thinning. I think he mentions to make any real change to the cross sectional geometry thin 1/3 way up the blade. Like you said tho every knife is different. Removing scratch patterns is basically just getting the scratches even and uniform where you thinned to get the knife back to an aesthetically pleasing finish.
     
  7. Mar 18, 2019 #7

    lemeneid

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    I think one piece of advice that gets ignored too often is don't thin unless you are confident of executing the job OR if you can afford to "screw up" the knife. Taking steel off and removing scratches is easy, fixing an overgrind or hollow in the bevel is NOT!!!!!!

    Also correct me if I am wrong, I think generally only thin knives with shinogi or blade roads. Unless you're a masochist, I think no one really attempts to thin zero grind knives or knives with super fat convexes.
     
  8. Mar 18, 2019 #8

    stringer

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    15529161576168869281939028304530.jpg

    Here's some examples.
    These are all on my thinning agenda for today. I've drawn a line with a sharpie where I'm going to target. Each knife is different. The cleaver on the far left is hella thin. Just need to thin a little behind the edge. The next two are original creations that are just still too chunky. So I'm thinning pretty much the entire face. The next is a Watanabe. I broke the tip. So I need to repair that and then polish where I've already been thinning. The next two are sort middle of the road in terms of how high up I need to thin. I wouldn't get to worked up about making scratch patterns disappear. Thinning should be something you are conscious of throughout the life of the knife or you will have problems. You can always even out your scratch marks with sand paper. I don't usually bother. I am going to eventually do that with my wife's Gyuto. It's been thinned a ton over the years. It needs to be re etched.

    15529165995536205665255100267278.jpg

    1552916636145869681239727020788.jpg
     
  9. Mar 18, 2019 #9

    mikaelsan

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    im not following 100%, but generally i feel like directly behind the edge is the most important, but the next about 20mm as almost just as important, i try and focus on that roughly 20mm. as for removing the scratch pattern, i would assume "they" refer to everything you have scratched on the knife in the process. if your doing freestyle thinning or convex, your likely going to have to polish out the scratches a little further up for every new stone you use to get rid of everything, because you will always end up scratching a little further up then you meant to do. As for a flat or concave wide bevel, your working with a much more controlled bevel, and you can get away with just dealing with just that
     
  10. Mar 18, 2019 #10

    PappaG

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    Ok, I'm getting there..somewhere slowly.
    Lets say I've decided to thin 1/3 up the blade because I think it will help my knife perform better. I start with a shapton 120 then 220 to thin.
    Lets further assume I have a full progression of stones up to 6000. Would you take all the way up? It depends? I just get stuck/hung up when posters say they are removing or refining a scratch pattern and what exactly such statements mean. I appreciate the responses.
     
  11. Mar 18, 2019 #11

    HRC_64

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    Try to identify where in the geometry the problem is, and then work your way to the problem and stop when its gone away.

    eg, if you have a hard-shoulder right behind the edge...take this off
    eg2, if you have a "thick tip" and need to put in some distal taper...then take out metal higher...to the spine
    2g3, if some issu is "in-between" etc, do test cutting to identify where you are getting problems and mark with sharpie.

    analyzing the grind is a bit of a skill/experience thing ...
    but sometimes very small changes will make ∆s in performance.
     
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  12. Mar 18, 2019 #12

    rickbern

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    I’m not the be all end all in thinning advice, but I do usually thin new “chunky” knives and others I’ve sharpened a bunch.

    I’d be really cautious about starting with a 120 grit stone. When I first started thinning I used a 400, as I got more experience I use a 220 a fair bit more. I’ve never found myself wishing I had a 120.

    I think a lot of this is controlled not just by angle but also by how high up the blade you place your fingers.

    I’m not great at cosmetics but I think sandpaper is easier after the 400 stone.
     
  13. Mar 18, 2019 #13

    Elliot

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    Couple notes:

    1. Everyone saying that it's relative is 100% correct. I, like many, listen to Broida and typically look for around 1/3. However, the key here is performance. Don't remove too much steel. Play with the knife for a couple more weeks and then go in again if it isn't performing where you want it to.

    2. I think 120 grit is a little coarse, but I tend to be conservative. I typically start at Chosera 400 for the first round because, again, I don't want to remove too much before I have taken the new wheels on a spin. Hope that makes sense.

    Personal recommendation to follow, but please take with a grain of salt. Jon and people like him have forgotten more about knife maintenance and all that than I will likely ever learn.

    - Ignore aesthetics until the job is done.
    - For your first session, I think you can get by with 400 grit and then 1k. Yes, it won't look pretty. It doesn't matter yet.
    - Use the knife for a while to see if it is performing as you would like.
    1. If no, repeat procedure.
    2. If yes, you can sandpaper or do whatever else you want for the sake of it looking nice.
    Again, by no means is anything I have said gospel. But hopefully useful.
     
  14. Mar 18, 2019 #14

    foody518

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    Here's an example in context of a thinning/removing highs and lows on a chunky wide bevel knife:
    -120 grit
    -400 grit
    -1000 grit
    -4000 grit
    etc.
    For a stone that follows another stone, I care that I have erased the scratch pattern created by the previous stone and replaced it with the scratch pattern of the current stone. You do not want to end up on your medium grit stone with still 120-220 grit scratches on any section of the blade where you were purposely trying to remove metal for your sharpening session. If you were also going for aesthetics, it sucks to see deep coarse grit scratches on the core steel under the lamination line by progressing prematurely to your finishing grits. This is a factor of time spent sharpening and also the relative capabilities of certain stones themselves, and you learn what works together in a progression and what your patience is for how long you are willing to spend on a stone to get a job done.
     
  15. Mar 18, 2019 #15

    Foltest

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    I would start with 120 only if I knew there is ton of material to be removed, like in case of chips and such. My usual process is to take 1K stone, do a few strokes to get idea what the blade is like, and then switch to 400, possibly something coarser if if I felt like I need to. Finish depends on the knife, nothing wrong leaving it on 400 grit finish. As egolan mentioned, test driving the knife before final finish is great idea.
     
  16. Mar 19, 2019 #16

    pd7077

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    Thinning is definitely variable and will depend on the type of knife you are working on and the goal that you want to achieve. You can certainly thin using a medium-coarse grit stone (i.e. 500-1000),but it won’t be as aggressive as a coarse stone (i.e. less than 500) so it will take more time and effort. This is probably the way to go when starting out as there is more margin for error. Once you feel more comfortable with the process, then you can try thinning with a coarser stone.

    My approach to a wide bevel will be different to that of a convex narrow bevel. Wide bevels are somewhat more straight-forward, but working out any overgrinds can often be very time consuming. You want to make sure that you’re working with a flat stone, and it is especially helpful if that stone is slow to dish.

    On the flip side, I like using softer stones when thinning a convex narrow bevel because that dishing will make it easier to maintain the convexity of the grind. Here is a Hiromoto AS 240 that I am working on for a friend. I did a bulk of the thinning on a very soft coarse 150 grit stone. A majority of the thinning was done on the bottom 1/3 of the blade with a focus directly behind the edge. I followed this up with a progression of 500, 1k & 2k. This was primarily to clean up the scratch pattern on the hagane because my plan was to clean up the cladding with a sandpaper progression (up to 600 grit) prior to etching. Here is a before & after and also a photo after I cleaned up the cladding.
    [​IMG]
    [​IMG]
    I am also working on a Hiromoto AS 270 for another friend that is a lefty. Here is the before & after. Since this one belongs to a lefty, I focused a little bit more on the left side in order to create a bit more convexity on that side for him. Again, using a softer stone that was dished made this process a whole lot easier.
    [​IMG]
    There’s no substitute for practice, and you’ve gotten a lot of good advice from the fellas here so I say you just go after it and start thinning!
     
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  17. Mar 20, 2019 #17

    bennypapa

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    How do you like the bevels on that #2 cleaver on the right? Mine is weird and it will be a few thinning sessions until I'm happy with it. The main bevel was a hollow grind on a much too small diameter wheel for my taste. That grind transitioned into a secondary bevel that was kinda fat. I've had 1 good go at it trying to get things into shape and thinner to my tastes but it's slow on stones.
     
  18. Mar 20, 2019 #18

    stringer

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    I've had it for several years. Never did much with it. Used it here and there, light sharpenings occasionally. Then I needed something to hack a frozen turkey apart with over Thanksgiving. I really jacked it up. So I decided to sharpen it to zero edge, thin it out. I already know I will have to put a sturdy micro bevel on it when I'm done or it will be useless. The steel is very soft. I'm using it as an opportunity to test out some stones. King deluxe 3k and crystolon coarse. The knife came from the Wok Shop about 10 years ago.
     
  19. Mar 20, 2019 #19

    Ruso

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    As low as I can handle the knife on a stone. Usually ends up somewhere around 21/50 of the knife.
     
  20. Mar 22, 2019 #20

    SilverSwarfer

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    Note: if you can stand the aesthetics, there is some benefit to be gained in not polishing out all the scratches from thinning. There is some good food release benefit in the texture. Alternatively, you can reintroduce texture uniformly and aesthetically pleasingly by using sand paper. And time. Don’t forget a lot of precious time!
     

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