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Thread: Pm-v11 at 20*

  1. #31
    Quote Originally Posted by Derek Cohen View Post
    Ken, Sellers’ technique may resemble the rounded, buffed edge of the “Unicorn” micro bevel, but it is not the same at all. He is not rounding and increasing the angle at the micro edge; he is simply working the full face of the bevel in a curved action. He takes care to avoid lifting beyond (say) 30 degrees at the edge.

    Regards from Perth

    Derek
    Derek,

    I probably should have put a "/s" or something to indicate my tongue was at least partially in my cheek but it is interesting that some convexity might be good. Sure goes against what many of us, including me, have been saying. But it may also confirm what I've been on my soapbox about for some time, the importance of smoothing the edge, not just making it shine, but smoothing it is more important than a perfect meeting of two flat planes.

    ken

  2. #32
    Quote Originally Posted by Steve Voigt View Post
    Hey Ken,
    I'd never say P.S. is a joke, though I'm not a huge fan either. But more to the point, the "unicorn" seems to me to have some key differences from Sellers's method. His is a smooth convex curve along the whole length of the bevel, maybe 3/8" or so depending on the thickness of the steel. The convexity Dave and Winston are describing is happening over something like .005", and if there is a steep (e.g. 45°) angle at the tip, it's only in the final couple thousandths.

    Steve,

    Correct me if I'm wrong, also part of their experiments is the use of a very shallow bevel to lessen the wedging effect. The Sellers comment was with tongue slightly in cheek, I've been as guilty as many on this forum of being shocked, I tell you shocked, of someone having a convex bevel and/or using a buffing wheel.

    BTW, One of the things I've learned well over my many years of teaching is how to eat crow.

    ken

  3. #33
    Quote Originally Posted by ken hatch View Post
    Steve,

    Correct me if I'm wrong, also part of their experiments is the use of a very shallow bevel to lessen the wedging effect. The Sellers comment was with tongue slightly in cheek, I've been as guilty as many on this forum of being shocked, I tell you shocked, of someone having a convex bevel and/or using a buffing wheel.

    BTW, One of the things I've learned well over my many years of teaching is how to eat crow.

    ken

    Ken,
    My bad; I should have picked up the tone of your comment. The Internet is where sarcasm goes to die.
    Correct on the bevel, as far as I understand it. Dave's hi-mag pics show a very steep bevel, 45-ish, transitioning to around 25 over about .005", and then farther back giving way to a primary bevel around 20. The steepest part, the part that's 45-ish, is maybe .001". So the steep part provides durability, but there's no steel behind it to act as a brake, so effort is reduced.
    If you go to around the four-minute mark in Dave's video ( https://www.youtube.com/watch?v=kH3deOUmCPg ), you can see it for yourself.
    "For me, chairs and chairmaking are a means to an end. My real goal is to spend my days in a quiet, dustless shop doing hand work on an object that is beautiful, useful and fun to make." --Peter Galbert

  4. #34
    Join Date
    Aug 2014
    Location
    Silicon Valley, CA
    Posts
    1,048
    Quote Originally Posted by ken hatch View Post
    ... Correct me if I'm wrong, also part of their experiments is the use of a very shallow bevel to lessen the wedging effect. The Sellers comment was with tongue slightly in cheek, I've been as guilty as many on this forum of being shocked, I tell you shocked, of someone having a convex bevel and/or using a buffing wheel. ...
    I'd say *one* of their experiments is with a shallow bevel. I don't think we should make definitive statements about their results as they've branched in several directions with their efforts. One of the interesting things, to me listening and watching, is in their small way they are "doing science". One reports "I did this and got this result" and another tries to reproduce that result and often thinks of and tries a variation.

    Like science it's messy and will be easier to understand in hindsight, but... I think they got started when David Weaver, who uses a shallower than typical bevel angle anyway, said to himself this cheap chisel sucks, noticed his buffer, and wondered if it would improve the edge without much effort. It did, much more than he'd hoped for. Others explored the cheap chisel improvement while others tried taking better chisels to bevel angles outside their comfort zone. While doing that other buffer solutions and alternates to buffer solutions, e.g. strops and altering tip angle on finishing stones, are also being explored.

  5. #35
    Quote Originally Posted by Steve Voigt View Post
    Ken,
    My bad; I should have picked up the tone of your comment. The Internet is where sarcasm goes to die.
    Correct on the bevel, as far as I understand it. Dave's hi-mag pics show a very steep bevel, 45-ish, transitioning to around 25 over about .005", and then farther back giving way to a primary bevel around 20. The steepest part, the part that's 45-ish, is maybe .001". So the steep part provides durability, but there's no steel behind it to act as a brake, so effort is reduced.
    If you go to around the four-minute mark in Dave's video ( https://www.youtube.com/watch?v=kH3deOUmCPg ), you can see it for yourself.
    Thanks Steve,

    Interesting video,

    ken

  6. #36
    Join Date
    Mar 2015
    Location
    SE Michigan
    Posts
    3,222
    I’ve done a few chisels the Seller’s method, and frankly, it produces a very nice edge. Downside is you really can’t use the chisel bevel side up easily, if at all. It’s an easy way to freehand a decent edge. Now, everything gets hollow ground first.

    At some point, I decided to take a few two cherries chisels down to 15* to use for paring. Didn’t work out too well. They quickly chipped which you can see if you enlarge the picture...especially the entire corner on the smaller size chisel. Could be my technique, but I plan to re-hone to 20* and give them a try.

    82D8A838-A237-4166-B6C8-694429869D10.jpg

    P.S. I think this was my first attempt at hollow grinding...and you can see by the middle chisel, I was challenged to say the least!
    Last edited by Phil Mueller; 07-30-2020 at 8:11 AM.

  7. #37
    Join Date
    Feb 2014
    Location
    Lake Gaston, Henrico, NC
    Posts
    8,973
    Here's a picture of another, newer Boxwood handled Marples chisel at 20 degrees. It's helping to reshape the profile on a molding plane made in 1735. I don't spend much time thinking about sharpening theory. I get paid to produce work, and usually am not going slow enough to teach lessons. Picture taken by friend with my phone. The biggest trouble was she couldn't keep from putting it between my eyes, and my hands. All my cutting edges are simple intersections of flat planes. I manage to get by.

    IMG_1986.jpg

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