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Grinds on Kitchen Cutlery

Discussion in 'Shop Talk - BladeSmith Questions and Answers' started by TheOTBalisong, Jul 5, 2012.

  1. TheOTBalisong

    TheOTBalisong

    288
    Jun 28, 2012
    What is usually preferred on Kitchen Knives, Hollow, or Chisel Grinds?

    Any feedback is appreciated, thanks.
     
  2. jawilder

    jawilder

    Jun 27, 2006
    I asked this question a while back on another forum and the general decision was that full flat grind is best. I also add a convex edge that goes up 1/8", and finish it with my paper wheels. I also take the edge down to .007 before I sharpen, so it gives me a tiny hollow edge, then short convex, then full flat to the spine.
     
  3. watercrawl

    watercrawl

    422
    Jun 2, 2006
    Very broad question, probably best answered a bit more narrow.

    Definitely not hollow and definitely not chisel grind (unless you're talking traditional Japanese knives...but even then it's more complex than a chisel grind).

    A very slight, symmetric convex grind is preferred by some....others prefer a true symmetrical flat grind with a convex edge as Jason has described....still others prefer a full flat grind spine to edge. I'm sure there are other similar grinds that are preferred as well.

    What I feel is more important than picking from those grinds, and Jason eludes to this, is that it needs to be thin. 0.010" or less at the edge pre-sharpening is best with a spine somewhere around 0.10" thick at it's thickest....a 0.20" spine even with a 0.010" edge is still not a good cutter. These are all chef's knives specs...other knives will vary depending on use.

    And since we're so thin....it has to be ground well with no "holes" in the grinding. "Holes" are what I call overgrinds along the edge where either side is thicker and the "hole" is thinner. As you sharpen into this section you will see the hole and it becomes an issue.

    Now, if you want to get fancy, smancy...a very slight convex in an asymmetrically ground knife can be fun too. Most traditional Japanese chef's knives (gyuto's) are ground asymetrically with something along the lines of 30/70 or 40/60 grind.
     
  4. Salem Straub

    Salem Straub KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Oct 20, 2008
    I agree with watercrawl on all that. A good synopsis of what cuts. Thin is the most important- with any modification in grind beyond a full flat being usually slight convexity aimed at improving food release.
     
  5. seionage

    seionage

    398
    Oct 3, 2010
    wow. So, am I reading you correctly, that the spine is slightly thicker than 1/64"? Also, what about a paring knife? What thickness at the spine?

     
  6. watercrawl

    watercrawl

    422
    Jun 2, 2006
    No...the spine would be 0.10" thick....1/10th inch.

    A paring knife....I'll shoot for 0.075" thick at the thickest....quick taper down to 0.05" half way down the blade.
     
  7. seionage

    seionage

    398
    Oct 3, 2010
    ahh...I feel like an idiot. I read your post to fast. thanks for clearing that up.
     
  8. JMJones

    JMJones

    859
    Jul 14, 2010
    I agree with watercrawl as well, I would also like to add that if you make a large chef knife and start with a .1 inch spine and a do a full flat grind and full distal taper, you will end up with a knife that flexes way too much. with such thin stock a very gentle distal taper or only tapering half of the blade helps alot.
     
  9. jawilder

    jawilder

    Jun 27, 2006
    Agreed. Mine isn't fully flat until about 3" after the heel.

    Also, make sure you heat treat BEFORE you grind the bevels to reduce the risk of warping. Although it sure is a bugger to get all the scratches out of 62HR steel. I was working on it last night and just couldn't get it flat like I wanted, so I decided to draw file it - WRONG! My files wouldn't even put a scratch in it. It takes sharp belts, slow speed, and patience.
     
  10. TheOTBalisong

    TheOTBalisong

    288
    Jun 28, 2012
    Good insight, I wanted to ask a fairly broad question, so as to get some interesting responses. I've heard hollow grinds being used on Kitchen Knives, which surprised me a bit, So I was wondering what the general opinion was on that topic, Thanks everyone.
     
  11. cbr900son

    cbr900son

    Mar 3, 2011
    Yu can use any grind you want but is it optimal for your needs is the thing.
     
  12. bluntcut

    bluntcut KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Apr 28, 2012
    Single bevel knives sometime hollow grinded the backside, e.g. Yanagiba.
     
  13. jdm61

    jdm61 itinerant metal pounder Knifemaker / Craftsman / Service Provider

    Aug 12, 2005
    For the hardcore kitchen knife nuts, the grind is EVERYTHING. Getting a knife to cut is not that hard........just make it thinner than you would ever have imagined possible. Convexing or, in the case of single bevel Japanese knives, the concaving of the flat back, is primarily about getting food to release. When I did my first 280mm sujihiki, I forged and rough ground the blade to a bit around .100 and heat treated it. I then did a full flat grind until the edge was less than .050. I then started convexing the lower 35-40% of the blade from the edge up until I got the edge down to well below 10 thousands of an inch. Then I thinned and blended a bit by hand sanding for a fairly long time. The it got sharpened. That is actually a "thick" edge, but it works pretty well on a suji which is a slicing knife. You would want to go thinner if you were making a gyuto that the kitchen guys would call a "laser." A quick and city way to check your find is to lay the edge of a business card across the bevel and see where it touches.
     

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