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Thread: Objectifying edge quality

  1. #1
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    Objectifying edge quality

    How do you all gage sharpness?

    I have a couple of micro cameras, but setting all that up is a hassle.

    There is the thread method by Steve Elliott or Brent Beach, I forget which.

    Last wkd, I had some LV plate w 3M film, did some free hand swipes on a plane, and had good results-satisfied.

    But, can't help thinking, is there a more objective way besides the above, or hair shave, bouncing light, etc?

    My problem is that shop time is only a few hours on a weekend, so doing a lot of comparison plane/chiseling, and trying to remember what edge held better w which medium is really hard.

    Of course, nowadays, my shop has all varieties of media, and I'd like to know how you all judge between your different choices. Can you remember edge performance like that?

    Thanks, D
    David
    Confidence: That feeling you get before fully understanding a situation (Anonymous)

  2. one should always endeavor to keep ones edges as sharp as possible, but no sharper.


    does it cut? it's sharp.
    how sharp is possible? that depends on a bunch of factors. I'm sure that this thread will devolve to examine them in depth.


    suffice it to say if the tool performs as intended and produces a result that meets requirements it's sharp enough. sharpening beyond that is a waste of your limited shop time.

    pictures of edges do not cut wood.

  3. #3
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    Quote Originally Posted by David Ragan View Post
    My problem is that shop time is only a few hours on a weekend, so doing a lot of comparison plane/chiseling, and trying to remember what edge held better w which medium is really hard.
    The only judging that matters is whether it cuts wood the way you need it to in order to accomplish whatever you are trying to do.

    There are about three million ways to get a blade acceptably sharp. There is probably a thread on each of them somewhere on this forum. If you have limited shop time, you should avoid wasting it on trying different methods. Pick one and stick with it. If your edge is not good enough to do what you want to do, don’t assume you need a different jig or magic stone or whatever. Just assume you need more practice.

  4. #4
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    Quote Originally Posted by bridger berdel View Post
    one should always endeavor to keep ones edges as sharp as possible, but no sharper.


    does it cut? it's sharp.
    how sharp is possible? that depends on a bunch of factors. I'm sure that this thread will devolve to examine them in depth.


    suffice it to say if the tool performs as intended and produces a result that meets requirements it's sharp enough. sharpening beyond that is a waste of your limited shop time.

    pictures of edges do not cut wood.
    I'M from this school, but that's just my 2 cents!
    Rick

  5. #5
    I feel the edge with my thumb. With enough practice I found I can recognize when I have done a good enough job.

    Every so often I look at the edge with a loupe to find nicks that require grinding.

  6. #6
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    Quote Originally Posted by David Ragan View Post
    There is the thread method by Steve Elliott or Brent Beach, I forget which.
    http://bladetest.infillplane.com/htm...sharpness.html

  7. #7
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    I think the short answer is no. The most practical way is to attempt a task that requires a sharp blade. Taking a clean continuous end-grain shaving is a good benchmark. It's not terribly objective since the material properties of the wood play a large role, as do technique and equipment, but unless you are trying to build a scientific database or something I think that's irrelevant. As a woodworker you will have to manage all of those variables anyways. Of course there are other tests like cutting paper, shaving arm hair, severing a hanging hair.

    Experience will help, and over time the tendency is for edges to become sharper- your standards will get higher. Perhaps you can help the process along by keeping a certain piece of wood around for taking test cuts. Being the same piece of wood, you can gauge your relative sharpness to previous attempts. But mostly, just do work and observe how the cut feels, and how the tools leaves the surface.

    Something I have always done is touch the edge with my fingers after sharpening. With some experience I can tell instantly how good the edge is, if there's still a burr or wear bevel, etc, without having to shave arm hairs or test anything. If it doesn't feel right I go back to the stones until it does.

  8. #8
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    one should always endeavor to keep ones edges as sharp as possible, but no sharper.
    Interesting quip, but not one to garner my agreement. My sharpening is mostly to my perceived level of need. My axe doesn't need to be as sharp as my plane blades. My mortise chisel doesn't need to be as sharp as my paring chisel.

    While shooting some end grain a few days ago there were lines across the end of the piece being worked. This is an indication of there being some nicks in the blade. There was no need for fancy camera equipment to see the result of the nick. When the blade was removed and held under a lamp is was easy to see starburst reflections along the edge where the nicks occurred.

    Testing sharpness can be done many ways without fancy equipment. Mostly it involves experience in judgement.

    Paper Test:

    This is taking a piece of ordinary paper and pushing the blade into it. A sharp blade can go straight into the paper. If the blade is close to being 'sharp' it can cut the paper by moving the blade laterally across its edge. As you get better at sharpening you will find things like receipt paper needing a sharper edge to penetrate in a straight push.

    End Grain Test:

    Taking a thin shaving when paring end grain is an important ability when cutting dovetails, tenons and other joinery. Using a soft wood like pine is a good test. If the blade isn't sharp it will push and separate the fibers and it will be clearly visible. As stated above, little nicks in the blade will leave visible marks on the end grain. More than a test, this is also good practice at paring.

    Finger Nail Test:

    A sharp blade will stick with a very light touch on one's finger nail. How low of an angle can be used and still have it stick is a way to determine sharpness. Some folks will slide the end of their finger nail to check for burrs or nicks. This kind of makes me a bit squeamish. If you bite your nails, it may be best to not attempt this method.

    Arm Hair test:

    This is testing the shaving ability of an edge. There are a few different levels of sharpness that can be detected with this test. This test can be dangerous if one is not familiar with shaving with a straight razor or has difficulty controlling the edge of the tool being tested.

    If one can feel hair being pulled, there are still some nicks or burrs on the edge.

    If it feels like it is pushing the hairs over but a few cut hairs remain 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 many 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.

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

  9. #9
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    On sharpening media, use what you have. Unless you have poor quality sharpening equipment it isn't keeping you from getting to sharp.

    In Atlanta you may not have the freezing problem my shop has. This has me using water stones in warm weather and oilstones during the freezing months. Sometimes the oilstones get used when it is warm.

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

  10. #10
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    I just check the edge on my finger nail. If it sticks, it's good. If it skates, or even almost skates, not good enough.

    That said, for my jack plane, I'll sharpen upto my 1200 grit diamond plate and follow with stropping. Almost everything else gets sharpened up to 8000 grit on my ceramic stones and then stropped.

  11. #11
    Quote Originally Posted by David Ragan View Post
    How do you all gage sharpness?

    I have a couple of micro cameras, but setting all that up is a hassle.

    There is the thread method by Steve Elliott or Brent Beach, I forget which.

    Last wkd, I had some LV plate w 3M film, did some free hand swipes on a plane, and had good results-satisfied.

    But, can't help thinking, is there a more objective way besides the above, or hair shave, bouncing light, etc?

    My problem is that shop time is only a few hours on a weekend, so doing a lot of comparison plane/chiseling, and trying to remember what edge held better w which medium is really hard.

    Of course, nowadays, my shop has all varieties of media, and I'd like to know how you all judge between your different choices. Can you remember edge performance like that?

    Thanks, D
    If you're going to compare methods, you should keep a journal. Then you look up your results and don't have to remember them. Whatever method you settle on, sharp is as sharp does, as all the above posts advise. Experience often contributes to wisdom. You should try it, but take notes along the way.
    Fair winds and following seas,
    Jim Waldron

  12. #12
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    http://www.sawmillcreek.org/showthre...never-heard-of

    And there you will see mention of this: http://www.edgeonup.com/

    Yes indeed, a real life, mostly affordable sharpness Tester. The engineer in me wants one. The broke person with high dental bills and a new car to pay for says no. But really, $100 on amazon for one of the models.

  13. #13
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    Quote Originally Posted by Andrew Pitonyak View Post
    http://www.sawmillcreek.org/showthre...never-heard-of

    And there you will see mention of this: http://www.edgeonup.com/

    Yes indeed, a real life, mostly affordable sharpness Tester. The engineer in me wants one. The broke person with high dental bills and a new car to pay for says no. But really, $100 on amazon for one of the models.
    You wouldn't want the $100 model to answer this sort of question.

    The EdgeOnUp testers use the same method as Steve Elliott, meaning that they measure the force required to cut a standardized piece of synthetic thread. The "tester" is nothing more than a peak-reading scale with a thread-holding fixture on top. The $100 model has a precision of 25 g, but truly sharp edges can cut such thread at much less than 100 g, per EdgeOnUp's documentation (and confirmed by Steve's work).

    You'd want the $150 version with 5 g. resolution.

  14. Quote Originally Posted by bridger berdel View Post
    one should always endeavor to keep ones edges as sharp as possible, but no sharper.




    Quote Originally Posted by Jim Koepke View Post
    Interesting quip, but not one to garner my agreement. My sharpening is mostly to my perceived level of need. My axe doesn't need to be as sharp as my plane blades. My mortise chisel doesn't need to be as sharp as my paring chisel.

    jtk


    fair enough. however, "as sharp as possible" must take into consideration the job at hand. "sharp" with regards to an axe is completely different from "sharp" as regards a straight razor. if you doubt this hone an axe until it will shave. then use it to cut down a tree.

  15. #15
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    This plus some rayon thread would probably get the job done about as well as the $150 EdgeOnUp machine. Its precision is 0.05 N = 5 g. As an added bonus you can actually use it as a tension gauge!

    Here are a couple higher-end options that are more precise and more useful for other stuff (wider measurement range):

    https://www.amazon.com/Nextech-DFS50...H9B2A4WY4S8EJM
    https://www.amazon.com/HF-50-Digital..._&dpSrc=detail
    Last edited by Patrick Chase; 10-18-2017 at 7:48 PM.

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