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  • Opinions needed on shaper cutter shape.

    The cutter is used in a shaper attachment on a bridgeport mill. The material being cut is annealed 4140. The job is serrating chuck jaws used to hold castings in a cnc lathe.

    Cutter is made from an old HSS punch.



    What I would like your opinion on, is the shape of the buisness end. The current one is flat across the bottom and has 4 usable corners. This set up seems to work ok, but, I think it dulls to quickly. (sharpening is via surface grinder) Depth of cut is .005" every 8-10 strokes.





    The following pic. is what I would like to try next. They are the same with the exception of the bottom being concave instead of flat.



    So, which one would you suggest?
    YES, I'M GRUMPY ALL THE TIME!
    DEAL WITH IT!

  • #2
    Here is a sample of the work being done.







    http://www.youtube.com/watch?v=a9IU7xvTDeE
    YES, I'M GRUMPY ALL THE TIME!
    DEAL WITH IT!

    Comment


    • #3
      Serrations are technically no different than threads on screws - why not use a threading form?

      Comment


      • #4
        How about just making the grooves in the jaw much shallower (less cuts) to extend tool life, Iv never seen serrated jaws that.. pointy unless they are designed to be grabing meat or something
        Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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        • #5
          Rob is perpetrating a stealth brag. His serrations look just great and I think he knows it. I went out to look at my chuck jaws. They seem to have 90 included angles and about 1/6 depth root and tip flat.

          4140? Yeah it will HT to Rc 53 OK but I think the jaws will last longer if made from a plain high carbon tool steel HT to Rc 58. But you got 'em made so go with what you have. Save my persnicketies for the next set of jaws.
          Last edited by Forrest Addy; 07-30-2010, 01:24 AM.

          Comment


          • #6
            Rob,

            I would definitely go with the hollow ground one, which will not only cut better, but also reduce deflection in the cutting tool a bit.

            PM

            Comment


            • #7
              Shaper reading

              The OP's tool is a square and is vertical to the job and so has no front or side clearance angles.

              The tool being long and thin is probably too flexible which will only make the situation worse.

              Read here:
              http://www.neme-s.org/shapers/shaper_columns.html

              http://bbs.homeshopmachinist.net/showthread.php?t=37036

              Comment


              • #8
                First thing:
                Relief! The back just rubs and makes the cut look bad (last picture).

                Second:
                Make the face slanted, but only in one direction and then move the tool along one side of the groove (like in thread cutting) so it only cuts on one side. -> shorter length of cutting edge, less load, better surface


                Nick

                Comment


                • #9
                  Looks great to me.

                  I KNOW NOTHING ABOUT CNC. I am surprised to see that jaws as significant as that are needed in the cnc process. Those steppers must really move those projects around quickly to warrant the need for jaws?
                  - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
                  Thank you to our families of soldiers, many of whom have given so much more then the rest of us for the Freedom we enjoy.

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                  • #10
                    Make up a shank to hold a square carbide insert,four usable corners,easy to sharpen,positive rake built into the insert.SPG or SPGT insert might work.
                    Last edited by wierdscience; 07-30-2010, 08:31 AM.
                    I just need one more tool,just one!

                    Comment


                    • #11
                      Thank you for the responses.

                      First, let me correct a mistake in the original post. The material being cut is A-2, not 4140.

                      This was my first time using a shaper of any kind. The job was given to me due to the toolmakers and machinists being busy with more important jobs.


                      Serrations are technically no different than threads on screws - why not use a threading form?
                      Good idea, Never thought of it that way. Being an amatuer at this, I just copied the one used by the toolmakers.

                      How about just making the grooves in the jaw much shallower (less cuts) to extend tool life, Iv never seen serrated jaws that.. pointy unless they are designed to be grabing meat or something
                      Looks great to me.

                      I KNOW NOTHING ABOUT CNC. I am surprised to see that jaws as significant as that are needed in the cnc process. Those steppers must really move those projects around quickly to warrant the need for jaws?
                      As pictured, the horizontal grooves are turned on the machine that the jaws will be used on. They are then brought to this shop for the verticle grooves. They are used on raw rough castings. When I asked about the depth of the grooves, they told me that that was the way they make all of the serrated jaw inserts.

                      Rob is perpetrating a stealth brag. His serrations look just great and I think he knows it. I went out to look at my chuck jaws. They seem to have 90 included angles and about 1/6 depth root and tip flat.

                      4140? Yeah it will HT to Rc 53 OK but I think the jaws will last longer if made from a plain high carbon tool steel HT to Rc 58. But you got 'em made so go with what you have. Save my persnicketies for the next set of jaws.
                      Lol, thanks. No bragging here.

                      Sorry, that was a mistake. They are actually made from A-2 not 4140.

                      Rob,

                      I would definitely go with the hollow ground one, which will not only cut better, but also reduce deflection in the cutting tool a bit.

                      PM
                      That was my thinking also.

                      The OP's tool is a square and is vertical to the job and so has no front or side clearance angles.

                      The tool being long and thin is probably too flexible which will only make the situation worse.

                      Read here:
                      http://www.neme-s.org/shapers/shaper_columns.html

                      http://bbs.homeshopmachinist.net/showthread.php?t=37036
                      Thank you for the links. Still reading.

                      First thing:
                      Relief! The back just rubs and makes the cut look bad (last picture).

                      Second:
                      Make the face slanted, but only in one direction and then move the tool along one side of the groove (like in thread cutting) so it only cuts on one side. -> shorter length of cutting edge, less load, better surface


                      Nick
                      I was concerned about the roughness also. When I asked about it they told me that most of it burns off in heat treat.

                      You lost me after slanting the face. Care to explain further?

                      Make up a shank to hold a square carbide insert,four usable corners,easy to sharpen,positive rake built into the insert.SPG or SPGT insert might work.
                      Was thinking along this line also, but wasn't sure how well a carbide or ceramic insert would hold up with an interupted cut such as this.


                      Thanks again for the comments.
                      Rob
                      YES, I'M GRUMPY ALL THE TIME!
                      DEAL WITH IT!

                      Comment


                      • #12
                        You lost me after slanting the face. Care to explain further?
                        OK, I think it is called rake. Your initial idea with the hollow face should cut fine. But I doubt that it will hold very long. The tip at the corner will soon break off. But the way you feed in, it does have to look that way.
                        Now if you feed along the face of one of the sides of the serration (read no longer radial but some weird kind of tangential) the tool no longer has to cut on two faces, but only on one face. This allows you to grind the tool's face quite different. You ony need rake in one plane. You can even tilt the cutting edge to get a shearing action.


                        Hope that is much clearer now.


                        Nick

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                        • #13
                          After looking at the suggestions, I'd say Weirdscience has the best one. After making the shank/tool holder it will be easy to swap out inserts when one dulls.

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