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Thread: Bevels

  1. #1
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    Bevels

    I asked this question on another thread. What's with the multiple bevels, over the last couple or three weeks I keep seeing mention of primary, secondary, and even tertiary bevels. Most of the time Rob Cosman is also given credit as in "sharpened as Rob Cosman does". Why?

    Is it a honing guide thing? Although if I remember correctly Cosman free hands.

    I know, get the popcorn out but I'm curious as to the reason or reasons.

    ken

  2. #2
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    It’s what helps him make the large jump from 500/1000 to 16,000. He grinds, lifts up a little on the coarse stone/diamond plate, and then a little more on the polishing stone.

    FWIW, Charlesworth (who uses a guide) also uses a tertiary bevel. I know he did in his articles a decade or so ago and I believe he does in his latest videos.

  3. #3
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    Yea, Rob does. Working from home, it's given me some ..ummm free time?? while waiting for jobs to run. So, he's running a primary and a secondary as I would. Then on his finest stone, he'll run a third bevel angle. Then the ruler trick. With that said, here's a link to a video where he's talking about doing exactly this. The first 3 minutes or so https://youtu.be/okLIEoz00v0
    ~mike

    scope creep

  4. #4
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    I'm not sure it's anything all that new in general. (Probably you have time on your hands these days and just noticed.) Perhaps some are coining new terms to distinguish specific variations?

    To me, the concept seems sound & well known, though maybe not worth the trouble. If you reduce your primary bevel you can reduce wedging, but possibly create an edge that is too fragile in practice. With the secondary bevel you can strengthen the very edge, but keep the relief from wedging. (Rinse, repeat, you're at tertiary bevels. Or more.)

    (It is also, to me, the same concept of knife sharpeners when they talk about thinning behind the edge. Different words, same basic concept. Possibly different details.)

    On another forum David Weaver is going on about using a buffer with polishing compound to give a "micro-convex" edge. It seems, in his experiments, to improve edge longevity at very shallow bevel angles significantly. I'm have trouble imagining this is significantly different than the strop sharpeners get. Too much you dub the edge. Not enough you don't have any practical effect. It's conceptually close enough I won't get it figured out without hours of experimentation using equipment I don't have. (Probably won't, but....) BTW- I don't doubt their results. David's honest in his reporting, other's have tried and agree, plus a number of microscope photos show the different cutting edge profiles and different types of damage pretty well. I do doubt extra equipment, steps, and skills, is cost effective for me right now.
    Last edited by David Bassett; 07-23-2020 at 8:25 PM. Reason: typo.

  5. #5
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    Quote Originally Posted by mike stenson View Post
    Yea, Rob does. Working from home, it's given me some ..ummm free time?? while waiting for jobs to run. So, he's running a primary and a secondary as I would. Then on his finest stone, he'll run a third bevel angle. Then the ruler trick. With that said, here's a link to a video where he's talking about doing exactly this. The first 3 minutes or so https://youtu.be/okLIEoz00v0

    Mike,

    I watched the video. Cosman is a good instructor and if you follow what he is selling you will have sharp cutters. That said, I think there are better ways to get there and there were a couple or three times he made statements that were like fingernails on a blackboard to me.

    ken

  6. #6
    Quote Originally Posted by ken hatch View Post
    Mike,

    I watched the video. Cosman is a good instructor and if you follow what he is selling you will have sharp cutters. That said, I think there are better ways to get there and there were a couple or three times he made statements that were like fingernails on a blackboard to me.

    ken
    Inquiring minds want to know. Please elaborate.

  7. #7
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    Quote Originally Posted by Steve Mathews View Post
    Inquiring minds want to know. Please elaborate.
    Steve,

    Without watching again, his statements about cap irons, thick irons, and not letting the cutter over the edges of the stone. I'm sure there were several others but I'm old and forgetful. Bottom line, while doing it his way will result in a sharp cutter, as stated, I think there are better ways to get there.

    ken

  8. #8
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    Steve,

    I just wanted to add.

    I've spent a good part of my adult life instructing. Even when "instructor' was not part of my job title I still did a lot of teaching. Cosman is very good at it, he is quite impressive having developed and broken down his method of getting to a working sharp cutter so that the average guy or gal can come off the street and learn to sharpen freehand in an hour or two. That part is pretty impressive. My hat is off to him.

    ken

  9. #9
    Quote Originally Posted by ken hatch View Post
    Steve,

    I just wanted to add.

    I've spent a good part of my adult life instructing. Even when "instructor' was not part of my job title I still did a lot of teaching. Cosman is very good at it, he is quite impressive having developed and broken down his method of getting to a working sharp cutter so that the average guy or gal can come off the street and learn to sharpen freehand in an hour or two. That part is pretty impressive. My hat is off to him.

    ken
    I agree Ken. His techniques may not be perfect and he has confessed to that but they work. As a relative beginner to woodworking I could do worse following someone with lesser experience. Besides, Rob is a charismatic sort of guy and entertaining to watch on YouTube. His efforts with the Purple Heart Project is a big plus for me.

  10. #10
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    Quote Originally Posted by Steve Mathews View Post
    I agree Ken. His techniques may not be perfect and he has confessed to that but they work. As a relative beginner to woodworking I could do worse following someone with lesser experience. Besides, Rob is a charismatic sort of guy and entertaining to watch on YouTube. His efforts with the Purple Heart Project is a big plus for me.
    Steve,

    Once you know what sharp is, loose the bevels. Learn to use the whole stone, I think it is Stan Covington that calls it "hang ten", and while you can get away with making that big jump in grits you will find it works better to put something in the middle. The problem with doing that using Cosman's technique you would need four bevels and pretty soon you would end up with a convex bevel and what you really want is a single flat bevel. Remember the process is grind (if needed and it almost always is), hone, and then polish. Most folks do not spend enough time on their polishing stone.

    Just one more thought, shiny is not necessarily sharp. Some of the most prized finish stones will leave a hazy finish. That Shapton 16000 grit stone Cosman uses will shine so bright it can be blinding but when you look at the scratch pattern, it sucks.

    Good luck,

    ken

  11. #11
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    Rob Cosman rightly credits David Charlesworth for the ruler trick. It’s essentially a time-saving step to polish just the edge of the back of the iron.

    The rest of David Charlesworth’s technique is basically identical to the one Rob Cosman teaches engagingly on YouTube. The key difference is that David uses an Elipse-type guide, while Ron does it freehand.

    In my view, the Charlesworth method is a bit more exacting, and therefore more repeatable. To get Rob Cosman’s results it helps if you’re Rob Cosman. In contrast, anyone can learn, copy, and master the Charlesworth method of a secondary hone on the 800 or 1000 stone and tertiary polish on the 8000 stone. Once you do, you discover that this method is also devised to save time.

    Three bevels on the front, ruler trick on the back. $15 honing guide. Fast and reliable.

  12. #12
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    Dogma plays an important role in training.

    When starting out, you need *a method* that can be reproduced in your own shop.

    Simple approaches are easy to remember.

  13. #13
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    I use single bevels, and flat backs, nothing else. My two helpers, that can almost read a tape measure when they work together, and anyone else, can get a super sharp edge. None of my plane irons, and few of my chisels, have seen a grinder in years.

  14. #14
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    +1

    Same with me. a single bevel, and a flat back...back to work.

    Too many bevels in such a small area....soon turns into just a single, dull, curve....

    Even a Butter knife can be polished up nice and shiny....and still barely cut warm butter.....

  15. #15
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    Quote Originally Posted by Bob Jones 5443 View Post
    Rob Cosman rightly credits David Charlesworth for the ruler trick. It’s essentially a time-saving step to polish just the edge of the back of the iron.

    The rest of David Charlesworth’s technique is basically identical to the one Rob Cosman teaches engagingly on YouTube. The key difference is that David uses an Elipse-type guide, while Ron does it freehand.

    In my view, the Charlesworth method is a bit more exacting, and therefore more repeatable. To get Rob Cosman’s results it helps if you’re Rob Cosman. In contrast, anyone can learn, copy, and master the Charlesworth method of a secondary hone on the 800 or 1000 stone and tertiary polish on the 8000 stone. Once you do, you discover that this method is also devised to save time.

    Three bevels on the front, ruler trick on the back. $15 honing guide. Fast and reliable.
    Bob,

    I'm glad you have found a method that works for you.

    None do I find fast and reliable with each there is a yes-but factor. Of course as with all things wood YMMV.

    ken

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