+ Reply to Thread
Page 2 of 3 FirstFirst 1 2 3 LastLast
Results 11 to 20 of 23

Thread: Hollow Grind

  1. #11
    Join Date
    06-19-2010
    Posts
    1,062

    Re: Hollow Grind

    All the references I read indicate that the hollow grind is more fragile than the flat grind which I can understand.

    As I understand, most woodworking blades are made from either O1 or C2 tool steel. I remember reading somewhere that C2 steel is more fragile than O1 due to the higher carbon content because of the crystalline structure of the carbon. I cannot find the references now.
    Reply With Quote Reply With Quote  
    Share with Facebook  

  2. #12
    Join Date
    06-19-2010
    Location
    Gods country -- New England
    Posts
    7,893

    Re: Hollow Grind

    I am not familiar with C2 as being a steel.

    I believe it is a Carbide.

    Carbide is certainly more brittle than steel - and will chip easier.
    Art and Creativity - Collide with the Functionality of CNC - priceless
    Reply With Quote Reply With Quote  
    Share with Facebook  

  3. #13
    Join Date
    06-19-2010
    Posts
    1,062

    Re: Hollow Grind

    Quote Originally Posted by Leo Voisine View Post
    I am not familiar with C2 as being a steel.
    For you.

    http://www.lie-nielsen.com/mortise-chisels/
    Reply With Quote Reply With Quote  
    Share with Facebook  

  4. #14
    Join Date
    06-19-2010
    Location
    Gods country -- New England
    Posts
    7,893

    Re: Hollow Grind

    Quote Originally Posted by Johnboy View Post
    That is "A2" not "C2" -- big difference.

    A2 - tool steel - I have heard of. We use a lot of A2 tool steel as well as O1 tool steel. As a matter of fact I have been cutting O1 today and for the past week in one of my machines.

    A2 at the hardness they spec out is certainly going to be brittle, but not like carbide. It's also going to be a little more difficult to sharpen - but doable.

    My Lee Valley chisel set is A2. Good stuff for sure.

    Either way - both materials have a high carbon content. That is what makes them through hardening - and also brittle.

    Hence, the low carbon steel and case hardening I was talking about before. The Japanese woodworker of years past (I don't know about now) realized that through hardened steels left a brittle edge. They opted for the "toughness" of a softer core and a case hardened edge.

    But case hardening on chisels does not fit well into this discussion.
    Last edited by Leo Voisine; 06-30-2014 at 9:18 pm.
    Art and Creativity - Collide with the Functionality of CNC - priceless
    Reply With Quote Reply With Quote  
    Share with Facebook  

  5. #15
    Join Date
    06-15-2010
    Location
    Huntington Beach, California
    Posts
    4,990

    Re: Hollow Grind

    (I also use a Tormek.)

    Based on what I was taught in a sharpening class.

    I go through the Tormek procedure. It is a hollow grind. Effectively, the "hollow" is about the radius of the wheel used to make the grind.

    Usually, the Tormek process goes to a honing step on a leather strop (Wheel) to finish the edge. I deviate and go to water stones. On the water stones, I put a grind on both the keen edge and the heel of the chisel. Some will try to call this a micro bevel but it is not. The wet stone grind is at the angle of the Tormek grind. I'll take this grind to 8000 grit.

    Here is the advantage of the hollow process.

    As the edge starts to become dull, the hone of the Tormek will bring it back as much as a dozen times. Then a quick pass over the 8000 stone restores the edge for another batch of honing operations. I can usually go over the 8000 stone six or eight times before going back to the Tormek.

    The water stone after the Tormek leaves two shiny strips across the bevel of the chisel thus causing confusion about what actually is a micro bevel. When the two shiny strips meet on the face of the chisel it is probably time to think about going to the Tormek again.

    BTW - When I'm doing a lot of chisel work, I'll have the Tormek on the bench for honing tasks as I chisel away.
    Rich
    Huntington Beach, California

    Surf's up
    Reply With Quote Reply With Quote  
    Share with Facebook  

  6. #16
    Join Date
    06-19-2010
    Posts
    1,062

    Re: Hollow Grind

    Quote Originally Posted by Leo Voisine View Post
    That is "A2" not "C2" -- big difference.
    Sorry, my bad.
    Reply With Quote Reply With Quote  
    Share with Facebook  

  7. #17
    Join Date
    05-20-2014
    Location
    Perth, Australia
    Posts
    2

    Re: Hollow Grind

    Hollow grind vs flat grind? It depends on how you hone the edge.

    The advantage of a hollow grind is that the bevel can be self-jigging if you freehand the bevel - that is, if you run the hollow over the honing stone. This is an efficient and speedy process since there is little steel to remove. By contrast, this method on a flat grind will need to remove significantly more steel, and therefore it is slower and more work.

    The flat grind is generally maintained on a Japanese blade since the hard/soft laminations enable it to work essentially the same way as a hollow grind. That is, the soft iron backing abrades fast and all one is really honing is the thin but hard tool steel. There is nothing to stop one hollow grinding Japanese blades either.

    Most who flat grind will prefer to use a honing guide. The strategy then is to only hone a secondary bevel (You can do this on a hollow grind as well). A micro (i.e. small) secondary bevel is also efficient.

    Hollow grinds and flat grinds wear at the same speed. It is the edge of the bevel that wears, not what is behind it.

    For all intents and purposes, they are equally strong. The rule is to grind a bevel at 30 degrees if you plan to use it in a bevel down plane, or in a bench chisel that will be hit with a hammer. The exception is a mortice chisel, which receives heavier handling, especially prising and not just chopping. Leave the bevel flat and add a 35 degree secondary bevel.

    Regards from Perth

    Derek
    Last edited by derekcohen; 10-11-2014 at 4:47 am.
    Reply With Quote Reply With Quote  
    Share with Facebook  

  8. #18
    Join Date
    05-31-2010
    Location
    Sacramento, CA
    Posts
    5,842

    Re: Hollow Grind

    Hey Derek!

    Welcome to this forum. I've followed your blog and seen your posts on SMC for years. We're sure glad to have ya!
    Jason Beam
    Sacramento, CA
    Reply With Quote Reply With Quote  
    Share with Facebook  

  9. #19
    Join Date
    05-20-2014
    Location
    Perth, Australia
    Posts
    2

    Re: Hollow Grind

    Thanks Jason!

    Shouldn't you be tucked up in bed at this hour?

    Regards from Perth

    Derek
    Reply With Quote Reply With Quote  
    Share with Facebook  

  10. #20
    Join Date
    05-31-2010
    Location
    Sacramento, CA
    Posts
    5,842

    Re: Hollow Grind

    LoL!

    Probably - tho, it's only barely 10pm in california right now. And it's friday so the wife lets me get crazy
    Jason Beam
    Sacramento, CA
    Reply With Quote Reply With Quote  
    Share with Facebook  

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts