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Thread: Objectifying edge quality

  1. #46
    Andrew,

    OK, since you asked (or is it my inherent proclivity to teach, or perhaps it's pure vanity). Here is my go-no-go test apparatus based on Cliff Stamp and Steve Elliott. I run a piece of thread (Elliott says 40 Wt Coates & Clarke rayon) over a gap to a weight. Then I lower the edge being tested onto the thread over the gap. Slowly, straight down, no slicing. If the edge is sharp, it cuts the thread. If not sharp, it depresses the thread and raises the weight.

    So, how sharp? According to Elliott, if 40 wt rayon thread is used, the weight should be 65 - 100 grams. Since I did not know the weight or composition of my thread I chose a weight by trial and error until I got to a weight that would not allow a fresh single-bladed razor blade to cut the thread. Then I added one more 1/4" hex nut (5 grams more or less). That came to about 75 grams as it turns out. So, a new razor blade cuts the thread. If the edge being tested also cuts the thread, it is as sharp as a new razor blade. And so forth. If my standard is less than that, I can use a heavier weight (another hex nut or so) I already have a 100 gram weight that I plan to use when I obtain some 40 wt rayon thread. Here are the pictures. I Photoshopped them to hide the worst of my execrable workmanship. The thread runs from the spool over a UHMW sheave, over the gap, through another UHMW sheave with a pin in it to act as a pulley, and down to the weight. Don't laugh at the wing nut. It makes a convenient thread clamp. So, this was an afternoon's pastime. But it works more or less and does not cost $150. BTW, I could just have made a loop of thread and hung the weight from it, supported by the edge being tested. But where's the fun in that?

    DougSharp-Gauge-2.JPGSharp-Gauge-3.jpg
    Last edited by Doug Hepler; 10-23-2017 at 5:42 PM.

  2. #47
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    Quote Originally Posted by Doug Hepler View Post
    OK, since you asked (or is it my inherent proclivity to teach, or perhaps it's pure vanity). Here is my go-no-go test apparatus based on Cliff Stamp and Steve Elliott.
    You're just a teeny little spring away from something that can return continuous sharpness scores instead of go/no-go :-).

  3. #48
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    A good test for sharpness is the hanging hair test, but I can say with honesty that I have long stopped 'testing' my edges. I'm going to put them right back to work and that is a test in itself.

    I will try and notice however; is end grain being pared cleanly when need be? Is the shaving produced clean? Is the surface shiny? etc.
    Bumbling forward into the unknown.

  4. #49
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    Quote Originally Posted by Brian Holcombe View Post
    A good test for sharpness is the hanging hair test, but I can say with honesty that I have long stopped 'testing' my edges. I'm going to put them right back to work and that is a test in itself.

    I will try and notice however; is end grain being pared cleanly when need be? Is the shaving produced clean? Is the surface shiny? etc.
    +1 on this, the result is the best test there is of edge quality.

    jtk
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

  5. #50
    4-8 Power Eye Loupe is a pretty good tool in an experienced tool makers tool box..
    aka rarebear - Hand Planes 101 - RexMill - The Resource

  6. #51
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    Quote Originally Posted by Doug Hepler View Post
    Andrew,

    OK, since you asked (or is it my inherent proclivity to teach, or perhaps it's pure vanity). Here is my go-no-go test apparatus based on Cliff Stamp and Steve Elliott. I run a piece of thread (Elliott says 40 Wt Coates & Clarke rayon) over a gap to a weight. Then I lower the edge being tested onto the thread over the gap. Slowly, straight down, no slicing. If the edge is sharp, it cuts the thread. If not sharp, it depresses the thread and raises the weight.

    So, how sharp? According to Elliott, if 40 wt rayon thread is used, the weight should be 65 - 100 grams. Since I did not know the weight or composition of my thread I chose a weight by trial and error until I got to a weight that would not allow a fresh single-bladed razor blade to cut the thread. Then I added one more 1/4" hex nut (5 grams more or less). That came to about 75 grams as it turns out. So, a new razor blade cuts the thread. If the edge being tested also cuts the thread, it is as sharp as a new razor blade. And so forth. If my standard is less than that, I can use a heavier weight (another hex nut or so) I already have a 100 gram weight that I plan to use when I obtain some 40 wt rayon thread. Here are the pictures. I Photoshopped them to hide the worst of my execrable workmanship. The thread runs from the spool over a UHMW sheave, over the gap, through another UHMW sheave with a pin in it to act as a pulley, and down to the weight. Don't laugh at the wing nut. It makes a convenient thread clamp. So, this was an afternoon's pastime. But it works more or less and does not cost $150. BTW, I could just have made a loop of thread and hung the weight from it, supported by the edge being tested. But where's the fun in that?

    DougSharp-Gauge-2.JPGSharp-Gauge-3.jpg
    Doug, that is an excellent gadget, I am fascinated and may be able to spend more time putting off critical WW cuts by making one.

    Last night, though, I was reading Chapter one of Leonard Lee's great book (we all know it) "Sharpening".......where the Wilkinson Sword razor blade's sharpness is outdone (photomicrographically) by a chisel honed on 6K grit, IIRC.

    How about that?
    David
    Confidence: That feeling you get before fully understanding a situation (Anonymous)

  7. #52
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    Quote Originally Posted by Doug Hepler View Post
    Andrew,

    OK, since you asked (or is it my inherent proclivity to teach, or perhaps it's pure vanity). Here is my go-no-go test apparatus based on Cliff Stamp and Steve Elliott. I run a piece of thread (Elliott says 40 Wt Coates & Clarke rayon) over a gap to a weight. Then I lower the edge being tested onto the thread over the gap. Slowly, straight down, no slicing. If the edge is sharp, it cuts the thread. If not sharp, it depresses the thread and raises the weight.

    So, how sharp? According to Elliott, if 40 wt rayon thread is used, the weight should be 65 - 100 grams. Since I did not know the weight or composition of my thread I chose a weight by trial and error until I got to a weight that would not allow a fresh single-bladed razor blade to cut the thread. Then I added one more 1/4" hex nut (5 grams more or less). That came to about 75 grams as it turns out. So, a new razor blade cuts the thread. If the edge being tested also cuts the thread, it is as sharp as a new razor blade. And so forth. If my standard is less than that, I can use a heavier weight (another hex nut or so) I already have a 100 gram weight that I plan to use when I obtain some 40 wt rayon thread. Here are the pictures. I Photoshopped them to hide the worst of my execrable workmanship. The thread runs from the spool over a UHMW sheave, over the gap, through another UHMW sheave with a pin in it to act as a pulley, and down to the weight. Don't laugh at the wing nut. It makes a convenient thread clamp. So, this was an afternoon's pastime. But it works more or less and does not cost $150. BTW, I could just have made a loop of thread and hung the weight from it, supported by the edge being tested. But where's the fun in that?

    DougSharp-Gauge-2.JPGSharp-Gauge-3.jpg
    How about a strand of super thin fishing line? Maybe the standards would be more consistent? I mean instead of thread being multiple strands wound together, you have a solid piece of line (polypropylene?).
    David
    Confidence: That feeling you get before fully understanding a situation (Anonymous)

  8. #53
    Quote Originally Posted by Johnny Kleso View Post
    4-8 Power Eye Loupe is a pretty good tool in an experienced tool makers tool box..
    Johnny,

    I agree, a loupe, a good light (direct sunlight is best), and your fingers are the best test for several reasons. The most important is the edge will degrade with first contact, testing starts that process.

    I have often said if it looks sharp and feels sharp it is sharp.

    ken

  9. #54
    David,

    I think fishing line would work well. (a) I wanted to use Elliott's experience as a basis and (b) there was no fishing line in my wife's sewing box

    Brian, Jim, Johnny, Ken, . . . I get it. But the OP was about objective measurement

    Doug
    Last edited by Doug Hepler; 10-24-2017 at 9:33 AM.

  10. #55
    Quote Originally Posted by Doug Hepler View Post
    David,

    I think fishing line would work well. (a) I wanted to use Elliott's experience as a basis and (b) there was no fishing line in my wife's sewing box

    Brian, Jim, Johnny, Ken, . . . I get it. But the OP was about objective measurement

    Doug
    Doug,

    Agree but all the paper, nail, end grain tests do not give an objective measurement. For that you need something like the "Edge on up" or better.

    Of all the subjective "tests" looking and feeling works as well if not better and has no downside.

    ken

  11. #56
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    Thinking about all the times someone has suggested my time was wasted rehabbing old tools when it would have been possible to buy new planes from our favorite sources and have been time and money ahead.

    Spending as much time as it takes to read this thread about coming up with a way to put a number on the quality of an edge seems to be a bit more frivolous with one's time.

    For my way of thinking there is a bit of a flaw with Doug's testing device. The thread is able to move laterally under the edge.

    My thought is the thread should not be able to flex. The thread should be fixed between two points that can move and pull on a calibrated gauge to determine how much pressure it takes to penetrate the thread.

    Again, to what end is all of this?

    As alluded to in an earlier post, the resulting surface produced by the edge is as good a test as any other.

    For me, a test on removing arm hair tells me a lot before walking away from my stones. At most the inconvenience involves rolling up my sleeves. The result can be broken down in to different levels:

    If the blade's edge rolls over the arm hair, it needs a bit more work.

    If one can feel hair being pulled, there are still some nicks or burrs on the edge. Some hair may be removed, but any nicks will leave streaks on end grain.

    If it feels like it is pushing the hairs over but a few cut hairs appear on the edge, then the blade is starting to enter the realm of sharp.

    If the blade is clearly removing hair but leaving a few behind, it is pretty sharp and would likely be able to take on most normal tasks.

    If it feels like nothing is happening but a pile of hair is on the blade and a clean swath is in its wake, then the blade is sharp enough for wood working. At least none of my edges that have done this have had any problems with any woodworking tasks of mine.

    Razor users would want sharper than this. They move to the hanging hair test. In this test the blade is touched to a hanging hair and the hair should separate by its own weight on the blade, or something like that. The hanging hair test also has a few different degrees of sharpness.

    So folks, save time and money by using what is growing on your arm.

    Warning this test is not for the squeamish or those with an unsteady hand.

    jtk
    Last edited by Jim Koepke; 10-24-2017 at 1:20 PM.
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

  12. #57
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    This is an excellent thread but I must say reading it gets me all stressed out because I seem to have an infinite number of things that need to be sharpened. I'm definitely of the sharp enough school. Too sharp is counterproductive - more damaging than sharp enough - as I think WF is implying. I always remove the wear bevel.
    "the mechanic that would perfect his work must first sharpen his tools.” Confucius

  13. #58
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    Quote Originally Posted by Jim Koepke View Post
    For my way of thinking there is a bit of a flaw with Doug's testing device. The thread is able to move laterally under the edge.
    Yes, that's correct. Any sort of slicing motion invalidates the result. With that said I think that with good operator technique Doug's device will be perfectly workable. It's not *that* hard to avoid slicing.

    As to the larger point of whether this is worth doing, I think it depends on how you plan to use it. It was worthwhile for the rest of us that Steve Elliott did something along the lines, because he created and published a uniquely useful and informative data set.

    There are a depressing number of "sharpness studies" out there that consist of somebody staring at ridiculously ambiguous 'scope shots and making unjustified pronouncements on that basis. Brent Beach is a habitual offender in that respect. If you're going to go to the trouble of publishing a blog about sharpening, then you'd might as well go to the trouble of figuring out how to actually measure sharpness, as Steve did.

    OTOH for an individual woodworker who just wants to get work done, no, I don't think it's justified. That's why I haven't done it myself.

  14. #59
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    Quote Originally Posted by Patrick Chase View Post
    Yes, that's correct. Any sort of slicing motion invalidates the result. With that said I think that with good operator technique Doug's device will be perfectly workable. It's not *that* hard to avoid slicing.

    As to the larger point of whether this is worth doing, I think it depends on how you plan to use it. It was worthwhile for the rest of us that Steve Elliott did something along the lines, because he created and published a uniquely useful and informative data set.

    There are a depressing number of "sharpness studies" out there that consist of somebody staring at ridiculously ambiguous 'scope shots and making unjustified pronouncements on that basis. Brent Beach is a habitual offender in that respect. If you're going to go to the trouble of publishing a blog about sharpening, then you'd might as well go to the trouble of figuring out how to actually measure sharpness, as Steve did.

    OTOH for an individual woodworker who just wants to get work done, no, I don't think it's justified. That's why I haven't done it myself.
    http://www3.telus.net/BrentBeach/Sharpen/index.html

    First, though, what is our goal when we sharpen a tool? It is not just a tool with the finest possible included angle at the edge. We could prepare a plane iron with a 15 degree included angle that would cut very well but would require resharpening after just a few feet of planing.


    Sharpness in tools means the right balance of edge sharpness and edge durability. We want to be able to plane several hundred feet between sharpenings.


    Finding the right included angle is a matter of experimentation. You can begin with a standard angle and experiment with larger and smaller angles and see which angle works best for the wood you are using and your style of working.


  15. I'm with Brian: I sharpen to get to work. I never sharpen to measure sharpness. I get a lot of work done that way.

    If I get tired of working, I'll stop and have a sandwich and a beer.

    You can carry on with measuring and posting; I'll get back to work.
    Fair winds and following seas,
    Jim Waldron

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