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Grinding/lapping/honing tiny bevels and corner roundings to cutting edges?

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  • Grinding/lapping/honing tiny bevels and corner roundings to cutting edges?

    On my quest to sharpen CBN inserts I was wondering what would be best home shop solution to bevel the insert edges?

    Beveling or "Y" in this pic is something like 0.004"

  • #2
    How critical is the "sharpening" (intentional blunting, really)?

    Just a rub on a diamond hone would probably do the job if you have the means to inspect the result.
    1601

    Keep eye on ball.
    Hashim Khan

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    • #3
      I guess, if you need any precision, it can be done on a surface grinder using a 20-degree fixture or sine plate, very fine grit diamond wheel and carefully approaching the edge. I'd try painting the edge with a marker and just touch the corner till the marker disappears along the edge.

      A quick and dirty calculation shows that the total wheel downfeed after the initial corner touch-up will be about .0013". Seems to be quite doable. A good magnifier will be needed.

      A low tech (and easier) approach would be to make a jig with a proper angle, set the insert edge protrusion (same .0013") and grind it against a diamond hone.
      Last edited by MichaelP; 12-11-2017, 12:35 PM.

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      • #4
        A Lansky knife sharpener system would do it.

        I bet it doesn't need to be that precise though, and that in reality you could just knock the edge off at approximately 20* by hand and get great results. I do this with a diamond lap on carbide inserts occasionally and found that the actual angle is not as critical as just getting an even and flat edge.

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        • #5
          Some of the manufacturer literature suggests pretty much that.
          1601

          Keep eye on ball.
          Hashim Khan

          Comment


          • #6
            Use a goniometer.

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            • #7
              Originally posted by MichaelP View Post
              I guess, if you need any precision, it can be done on a surface grinder using a 20-degree fixture or sine plate, very fine grit diamond wheel and carefully approaching the edge. I'd try painting the edge with a marker and just touch the corner till the marker disappears along the edge.

              A quick and dirty calculation shows that the total wheel downfeed after the initial corner touch-up will be about .0013". Seems to be quite doable. A good magnifier will be needed.

              A low tech (and easier) approach would be to make a jig with a proper angle, set the insert edge protrusion (same .0013") and grind it against a diamond hone.
              The insert has also something like 1/32" nose radius so that is added difficulty with surface grinder.

              I was thinking of hand-holding the insert on end of stick/rod and rotating it against lap.
              Result depends a lot on fine motoric skills as you would need to go by "feel" and timing, examining the results later with loupe/microscope.
              Or maybe something semi-soft would be even better "lap". Perhaps not quite buffing wheel. MDF (wood fiber board) wheels are popular among knife folks, maybe I give that one a try.

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              • #8
                Originally posted by elf View Post
                Use a goniometer.
                While a goniometer could be used, a goniostat is what you need They have been used since the mid 17th century for sharpening tool bits.

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                • #9
                  I'm trying to think of the name for a professional who uses one of these ginometer things...

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                  • #10
                    Originally posted by Yondering View Post
                    I'm trying to think of the name for a professional who uses one of these ginometer things...
                    That would be a bartender

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                    • #11
                      Originally posted by Yondering View Post
                      I'm trying to think of the name for a professional who uses one of these ginometer things...
                      Must be somebody from the Veterans Administration (VA). A well calibrated VA ginometer is indispensable.
                      Last edited by MichaelP; 12-13-2017, 12:59 AM.

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                      • #12
                        I think I want one of these.

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