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wavy shinogi lines

Discussion in 'Sharpening forum' started by Brad Gibson, Mar 18, 2015.

  1. Brad Gibson

    Brad Gibson Founding Member

    I was wondering if anyone could help with tips in fixing wavy shinogi lines in double bevel knives. I have a tanaka and a carter sujihiki that have small spots of wavy differentiating lines and I would like to fix them to look perfect. Or should I just send them to Jon?
     
  2. chefcomesback

    chefcomesback Founding Member

    Brad ,
    In my limited experience the wavy shinogi lines are result of both forging and grinding , if you leave an area thicker during forging , after heat treatment you are going to have to grind more that area to make it same thickness with the rest of the blade , this will result a wavy shinogi line and I think it is only cosmetic if it doesn't effect cutting . If you want to make it look even an "perfect "you may reveal the low spots on the edge resulting even holes , I will say leave as is
     
  3. Brad Gibson

    Brad Gibson Founding Member

    thanks mert
     
  4. JBroida

    JBroida Vendor Founding Member

    totally agree... on double bevel knives, perfect shinogi lines are rare
     
  5. NMaxy

    NMaxy Gold Contributor Contributor

    This same subject came up in Cris Anderson's thread. I'm curious why you value perfect, straight shinogi lines?
     
  6. Brad Gibson

    Brad Gibson Founding Member

    I guess its because I use single bevels primarily and just love the look of a sexy blade like a yanagi. I have a couple wide bevel sujis that have wavy lines and it bugs me. It doesnt effect performance so I guess I wont mess with them.
     
  7. MotoMike

    MotoMike Founding Member

    I like the look of the wavy shinogi lines. I see that some of the cheap knives even attempt to replicate it with some sort of surface treatment.
    A bit of discussion about why the single bevel have straight and double bevel do not would be appreciated.
     
  8. XooMG

    XooMG Founding Member

    A perfectly level blade with a perfectly level bevel will have an even shinogi. Waviness comes from warping or inconsistent thickness. Double bevel blades with kurouchi or textured finishes are usually not flattened perfectly. Given that a double bevel will usually have a more obtuse angle between hira/kireba, the wobble will be more obvious, and will be harder to eliminate completely. It's not impossible, but requires a good deal of rougher hand work (a good modern grinder and technique can reduce that work a lot), and doesn't really benefit the knife functionally.

    On thick-thick blades and single bevels and pieces with more diamond-ish cross section, it is quite a bit easier to accomplish a clean shinogi, though still not effortless.
     
  9. Rick

    Rick aka Pensacola Tiger Founding Member Gold Contributor

    Just so there is no confusion about what a shinogi line is, it is the transition line between the kiriba (blade path or road) and the blade face, as shown in this illustration from zknives,com. It is not the often wavy line that is formed at the intersection of the core steel (hagane) and cladding (jigane) as the kiriba is ground and polished.

    [​IMG]
     
  10. MotoMike

    MotoMike Founding Member

    Thanks Rick. I can't see your pic
     
  11. Rick

    Rick aka Pensacola Tiger Founding Member Gold Contributor

  12. MotoMike

    MotoMike Founding Member

    Rick
    when I click that link I get an access denied with go to main page message. when I find the link in question, the path is a bit differnent. see below. when I click that link in my post it goes right to it. Assuming this is the image.
    http://zknives.com/knives/kitchen/misc/jbladeant.shtml

    jbladeant.jpg
     
  13. MattS

    MattS Founding Member


    After all these years....I always wrongfully assumed it was the intersection of the cladding and core. Thanks Rick!
     
  14. CrisAnderson27

    CrisAnderson27 Professional Craftsman

    When rough grinding my knives, a perfect shinogi is a non issue. It is simply a matter of belt speed, pressure, and rate of movement across the belt. Anyone who has made a sword with little more than files understands how this works. A grinder is nothing more than a big, mean file...on steroids...with a dose of crack to boot.

    20140815_164021.jpg

    It's when things come to the final polishing that I have issues lol.

    One way I combat this is to grind the kireba (as well as the blade face, if it's not a compound grind) vertically as well as horizontally. This allows me to easily correct hollows I might have left in the kireba caused by too little speed, or too much pressure when grinding horizontally.

    I can honestly say that without exception, there are never, ever hollows in my kireba. Any issues I have with the shinogi come from poor hand polishing technique :).
     

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