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Thread: Hollow Grind

  1. #21
    Join Date
    06-20-2010
    Location
    Gods country -- New England
    Posts
    7,921

    Re: Hollow Grind

    Derek - Welcome to the forum - thank you for your posting
    Art and Creativity - Collide with the Functionality of CNC - priceless
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  2. #22
    Join Date
    12-14-2012
    Location
    West Plains, MO, USA
    Posts
    103

    Re: Hollow Grind

    Quote Originally Posted by dcarter636 View Post
    Considering that just about everybody is going to hone that edge on a flat stone or wheel; flat grind vs hollow grind has no impact on edge durability. A hollow ground edge can however be honed quicker because you need to remove less material to make the actual fine working edge. The geometry behind 1/64" from the final edge does not influence on edge durability in any way.


    My comment assumes that a fellow knows what final edge angle he needs and grinds accordingly.
    Mr. Carter has stated the salient point in the flat vs. hlw-grind debate.
    I recently got the Grizzly low-spd wet grinder w/lthr stropping wheel. I can now state publicly that flat ground/honed ain't sharp.
    I used to think I got a nice edge with a pc of plate glass, spray adhesive, & good sandpaper, & I did, but it takes less than 1/3 the strokes on a 3000 grit water stone (I counted) to re-establish the cutting burr on my chisels, planes, & riving knife since the hollow grind was applied.
    I may end up wearing these tools out fractionally quicker, but I 'm 60 yrs old & the grandkids kin buy their own.
    'Tis better to keep one's mouth shut and be thought a fool, than to open it and remove all doubt.
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  3. #23
    Join Date
    06-19-2010
    Posts
    1,093

    Re: Hollow Grind

    Since yesterday afternoon, I have been on a sharpening binge -- sharping all of Mom's kitchen knives, my chisels and plane blades. Mark was saying earlier in this thread that if your sharpening method isn't easy then one will procrastinate thus using tools that are a safety hazard by being dull. Yes, my Tormek is in the shop and yes I do have a gallon container of water for use so there shouldn't be any excuses until you read the next paragraph.

    Unfortunately something in my setup hasn't been right where the blades did not end up 90 degrees to the side of the chisel or iron. Everything I thought about adjusting didn't have any adjustment feature so it would have been brute force if anything; the jig was fixed, the jig holder was fixed -- was the holder warped -- don't think so. Was the jig defective -- could be but didn't want to just throw money at the fix. I knew I needed to touch up the blades however I wasn't sure what needed to be adjusted to bring it back into alignment so I procrastinated.

    Tormek recently upgraded their tool jig for sharpening flat blades that allows one to tweak the angle setting among other things (It also allows one to camber plane blades). Knowing my dilemma I bought one then proceeded yesterday to rectify two problems. The first problem was to square the edge and secondly change the grind from flat to hollow on my plane blades and you'll see why in a second.

    Some time ago I purchased the Tormek SJ-250 Japanese stone which is 4000 grit polishing stone. You're probably wondering why anyone in their right mind would buy such an animal. The leather strop on my Tormek wobbles somewhat and thus I find that, particularly on my smaller chisels, I get considerable round over on the majority of the edges. I also believe I've never gotten anything super sharp using the strop which is probably a operator error.

    So, I spent the better part of yesterday afternoon hollow grinding in prep to using the SJ-250 wheel. I can report that all the time and effort was well spent and I now have what I'd consider super sharp tools that are perfectly square.

    As a side note, I learned how to read the wave that is just ahead of the cutting edge to know if the blade will be 90 degrees or not. I also learned when to regrind the sharpening wheels.

    I'm confident now that I'll not wait so long next time to sharpen my tools. BTW, I also bought a new shaft that allows for faster removal/reinstall of the sharpening stones. This will allow me to store them in the house this winter and not worry about the water cracking them apart. And, not to be so reluctant to fetch the stone in the winter when I need to sharpen again.

    I apologize for being so long winded.
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