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  • Extreme closeup video of metal cutting

    Hi Everyone,

    It's been a while since I've been here, and no, I haven't finished my lathe milling attachment yet

    I saw this video and immediately thought of you guys. It is video taken at extreme closeup range of HSS and TiN coated HSS cutting mild steel and stainless.

    It's fascinating to see the metal bunch up on the HSS bit, while the cut still continues.

    http://www.youtube.com/watch?v=mRuSYQ5Npek&hd=1
    Lee

  • #2
    Waaay cool.

    Sort of makes me wonder how a person ever hits a + - .001" dimension.

    Dave

    Comment


    • #3
      Lee,
      A real interesting video. Something I hadn't ever seen before is how the workpiece material builds up on the tool tip and then randomly rolls under it. That could explain why once in awhile it's possible to get rough and smooth areas while machining on a lathe. And with even a slightly less rigid setup on longer parts, Then even very minor material deflection would only accelerate that happening. Many thanks for posting the link.

      Pete

      Comment


      • #4
        That first part looks like a cold chisel going thru a Snickers Bar.
        Gary


        Appearance is Everything...

        Comment


        • #5
          That's interesting, makes me wonder how we ever get a good surface finish on a part.
          It's only ink and paper

          Comment


          • #6
            Now if I could just grind my tools so that bit that builds up always breaks off and goes up, not down...

            Comment


            • #7
              We could talk about cutting tools
              But tearing tools might be more apt

              Comment


              • #8
                Polish Your Tools, Gentlemen

                It is indeed a very interesting video. First I have to wonder just how it was shot. I mean, how do you see a true cross section while the cutting is in progress. There must be some kind of clear (plastic? glass? whatever?) window to allow us to see it. What effect does that window have on the cutting process? It must have some.

                Another concern is the rake angle. They claim 30 degrees of rake for all of the shots and that is hardly a typical value for lathe work. At least not on my lathe with any tools that I have. The rake angle in the videos, as I would define it, looked like 45 or 55 degrees. I think it was the included angle of the tool tip that was 30 degrees. That is not what is normally called the rake angle. I would love to see similar videos at normal rake angles. Even at negative rake angles which are frequently used with insert tooling.

                All that being said, I think the really interesting area is under the tool bit and just behind the tip. You can see the variations in the surface being cut there. Assuming that the chip is around 0.010" thick, these variations seem to be in the range of one to several thousandths. And yes, the buildup at the cutting edge often tumbles under the tool and that disturbed metal is left embedded in the workpiece behind the cut. Clearly, when we measure a cut surface to a thousandth of an inch, we are only checking the tops of the hills. I have found that using abrasive strips after cutting on the lathe will rapidly reduce the diameter by half or one thousandth and then the rate of reduction is much slower as you continue to use that abrasive in the same manner. Again, clearly there are some hill tops that are rapidly removed and then we reach a more solid plane where a better finish is possible. This is clearly in agreement with my experience and many sources.

                At first I thought that the T.I.N. coating made things a lot better. But on playing it a second time I changed my mind on that. It is different with the T.I.N. coating, but I am not really sure it is better. The real conclusion that I would draw from this is a polished surface on the rake angle would perhaps be the best way to improve the surface finish. This may not be intuitive as this surface does not contact the finished part, but it seems that it is the buildup at the tip that causes the bad finish. If that buildup can be prevented by having the whole chip slide cleanly up and away, then the surface finish will be better. Far better. Polish your tools, gentlemen: POLISH your tools.
                Paul A.

                Make it fit.
                You can't win and there is a penalty for trying!

                Comment


                • #9
                  I don't think this was done at the usual cutting speeds, though.

                  Comment


                  • #10
                    Paul,
                    Since that video shows what I think is a long straight line cut, I'd guess it was done on a planner. I'd like to see the same done with the addition of coolant and or cutting oil. Since that would obscure what's going on, Then maybe thermal imageing would work? It would be really interesting to see the actual effects and exactly why it helps at the tool tip. Obviously easier material flow is the main reason. But just how much does it reduce the material tearing?

                    And I also think your 100% correct about the the cross section would have a great deal of effect since you have one side exposed and unsupported ahead of the cut. But it does show how seemingly solid metal reacts much like that candy bar already mentioned on a highly magnified scale.

                    It's a really clear and simple to see point why a finely finished tool edge can only help.

                    Exactly how you can sharpen any tool to prevent the material from rolling under the tool tip is the tough one. So cleanly shearing the metal without that tearing seems to be the main problem. Maybe our state of the art cutting tools and the recomended grinding angles and shapes still have a lot of room for improvement?

                    Adding some carbide, diamond tipped, and ceramic tool tips would also be more than interesting as a comparision to what's really happening.

                    Pete

                    Comment


                    • #11
                      I noticed there was no radius on the nose of the cutting tool.
                      Seems strange.
                      I always thought that you were supposed to have at least a 1/64 radius on the tool nose, unless cutting Aluminum or plastic.
                      I wonder how long those tools lasted, being that sharp.

                      Comment


                      • #12
                        Originally posted by KiddZimaHater
                        I noticed there was no radius on the nose of the cutting tool.
                        Seems strange.
                        I always thought that you were supposed to have at least a 1/64 radius on the tool nose, unless cutting Aluminum or plastic.
                        I wonder how long those tools lasted, being that sharp.
                        They show you side view cross section. So the tool may have any radius as seen from the top, but you look at it from the side.

                        Comment


                        • #13
                          Originally posted by MichaelP
                          They show you side view cross section. So the tool may have any radius as seen from the top, but you look at it from the side.
                          Yes, the idea of a small (1/64") radius on a tool tip is as viewed from the top. As viewed from the side, as these shots were, it should be as sharp as possible. But I did see a very small radius on the cutting edge as viewed in the videos. It was probably well under 0.001", at least when the cutting started. I believe that these shots show that having that radius as small as possible is not the most important consideration for a good surface finish. Instead, the best cutting action was clearly taking place when there was no or very little buildup on that cutting edge and ALL of the material above the tip was passing smoothly over the top edge of the tool. And the worst was when a relatively larger buildup was present or was in the act of passing under the tool. This tells me that the most important thing for a good surface finish is to have a very slick UPPER surface on the tool; that is the surface that the chip slides over. If part of the chip starts to stick then the surface finish seems to go to heck. I was surprised that the T.I.N. coating did not make a bigger difference. But I guess it has a bigger effect on tool wear than on surface finish.
                          Paul A.

                          Make it fit.
                          You can't win and there is a penalty for trying!

                          Comment


                          • #14
                            This video is on at least 4 forums I know of right now.

                            Comment


                            • #15
                              There was a similar video posted a few months back, but in that case, it showed how the TiN coating reduced the sticking on the top side of the cutting edge.

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