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  • #46
    Originally posted by sch View Post
    that dipping really hot HSS into water to cool it can induce microfractures at the thin edges, a POV supported by metallurgists at Carpenter Steel, a tool steel specialty company.
    We've discussed that rec.metalworking thread here many times. My recollection was that when he asked the guys at Carpenter Steel, they told him to dip the tool steel.

    The amusing part was when several folks pointed out that all grinders have dip pots, and that most machine shop books, including Moltrecht's Machine Shop Practice, tell you to dip the HSS to cool it between grindings. He said he was going to track down Dr. Moltrecht and ask him why -- the thread stopped there

    I agree with the point about HSS having red hardness in the 1200°F range, that should make it immune to as much heat as a bare hand can handle.
    Last edited by lazlo; 09-21-2012, 10:54 AM.
    "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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    • #47
      Grinding HSS

      Freehand grinding is good but simple guides produce better-looking results without a bunch of facets. This is one that I made from some HDPE.


      John Stevenson’s recommendation to use the diamond wheel on HSS and view it as an expendable has improved the quality and sharpness of my tools.

      With these grinding guides I Don’t use the overhead water pot but I do wet the table and guide which removes a lot of the heat and prevents the bit reaching a troublesome temperature.

      I rough out the bits on the 2X72 belt sander and finish on the grinding wheels.

      For grinding good threading tools using HSS cutoff blades I copied this setup from over on the PM Gunsmith forum.


      The wheel shown is CBN that Evan’s wife got for me.
      Byron Boucher
      Burnet, TX

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      • #48
        Originally posted by Boucher View Post
        Freehand grinding is good but simple guides produce better-looking results without a bunch of facets. This is one that I made from some HDPE.
        Nice job Byron.
        "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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        • #49
          At school the instructor says since hss is pretty much out dated, and we wont be covering it.
          That is a ridiculous statement. HSS tools are a part of the arsenal and will address cutting problems that cannot be solved any other way. You should print out this thread and take it to him, privately.

          I use everything from carbon steel tooling to diamond, ceremet and CBN cutters. They all have their advantages and disadvantages, uses and limitations.

          I'm just waiting for the Russians to start producing tooling with the trillion carat stockpile of superhard diamonds that they just declassified. The diamonds are a different crystal structure created by a meteorite impact and twice as hard as regular cubic diamonds.
          Free software for calculating bolt circles and similar: Click Here

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          • #50
            Originally posted by Dr Stan View Post
            The good ones do not. They use a stone or a steel just like my Dad the meat cutter taught me.

            Or even better yet, a leather strop like a barber uses or a leather wheel like a wood carver uses on a chisel.
            Or a paper wheel loaded with buffing compound. Or a 3M belt in the 5-10micron range.

            Ken

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            • #51
              Originally posted by Boucher View Post


              .
              O.T. -- But,
              I had the same problem fitting a box end wrench on the compound nuts
              when I had my Nardini. Nice fix.

              --Doozer
              DZER

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              • #52
                Many times I hear the best possible edge is from snapping a bit in half. Like when you shatter a endmill or break a bit off in the lathe. The edge of that break is normally razor sharp.

                I know nice formed angles aren't possible this way but has anyone ever tried making cleanish break and turned with it?
                Andy

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                • #53
                  Originally posted by vpt View Post
                  Many times I hear the best possible edge is from snapping a bit in half. Like when you shatter a endmill or break a bit off in the lathe. The edge of that break is normally razor sharp.

                  I know nice formed angles aren't possible this way but has anyone ever tried making cleanish break and turned with it?
                  Sounds similar to the process of napping flint for spear & arrow heads. I just do not know how one could control it enough to create the necessary clearance angles.

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                  • #54
                    The sharpest edge obtainable by any process is the edge of broken glass. The actual edge is one molecule wide. The standard for cutting exceedingly thin sections of tissue for microscopy is the broken glass microtome.
                    Free software for calculating bolt circles and similar: Click Here

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                    • #55
                      Adequate Sharpness

                      The cutting edge left from finishing with either CBN or a fine Diamond wheel is very good (almost like a mirror finish). If one is set up with guides and the table is left at the correct tilt, it only takes a second to refresh an edge. Try it , You will like it. The fact that the Tangential tools cut so good is related to the simple accuracy of their sharpening fixtures.
                      Byron Boucher
                      Burnet, TX

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                      • #56
                        Originally posted by Evan View Post
                        The sharpest edge obtainable by any process is the edge of broken glass. The actual edge is one molecule wide. The standard for cutting exceedingly thin sections of tissue for microscopy is the broken glass microtome.
                        You can make some splendid scrapers for wood that way too

                        Richard

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