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Carbide, HSS, and those old textbook deep cuts....

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  • Carbide, HSS, and those old textbook deep cuts....

    After the "carbide wars", and other discussins of lathe capabilities, it occurred to me that the old-timers seemed to have done much better than we do, despite our high-falutin' exotic grades of carbo-stellite-unobtanium with poso-negatory rake etc.

    I often take a pretty deep cut when using the lathe, finding that it produces less bending on the part if the tool is ground right.

    But....

    Some of those old textbook pictures show small lathes using lantern posts taking off a D.O.C. of what looks like 0.25" or better. You know, the picture with a large coiled single-piece chip coming off the part, and a real whopper of a diameter reduction. The chip does not look like it is a thin ribbon, either, it looks pretty substantial, at least several thou thick.

    Have any of you ever duplicated that sort of performance?
    1601

    Keep eye on ball.
    Hashim Khan

  • #2
    Yes. Next time I have the oppurtunity, I will take a video of my Pacemaker in action. I've not pushed it past .3 DOC (.6 off the diameter) but I've been told the larger Pacemakers could take a .5 DOC and not sweat it. It hums along like it's no big deal. You get a really nice surface finish, even on mild hot rolled steel when you take such a big cut. I was impressed, also, with the tool life. I could remove more material between sharpening taking large DOC than I could with smaller DOC.

    Of course the Pacemaker doesn't really qualify for little ...

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    • #3
      They're called full HP cuts. If there is stock to remove the management wants it removed expeditiously. I recall running two heads on a 1960 era King vertical boring mill. This machine didn't have side heads but the rail heads were plenty stout. We had several elevator winch drums to machine for a replenishment at sea project. We're talking 45" dia here.

      The machine had 75 HP and with both rail heads going I was removing a bit less than an inch per head at 0.070 feed or there abouts. The material was cast steel and machined beautifully - all 6's and 9's. You could fit about 4 to a coffee cup. As the chips flowed I shoveled them into an ever growing heap eventiually getting 3 ft high so some luckless apprentice could haul them off to the chip facility. The chips were still hot and radiated heat like a steam boler, so hot they scorched a hollow in the wood block floor about an inch deep.

      Whenever I had a cut like that going the bosses would gather and grin. It did make a good show. It was fun back in them days.
      Last edited by Forrest Addy; 07-16-2009, 02:43 AM.

      Comment


      • #4
        Hold on there.......

        PACEMAKER?

        That's cheating and you know it!

        I mean cuts like that on a 9 or 10 inch SB, Logan, Atlas, etc, the same kind of deal as the old texts.....
        1601

        Keep eye on ball.
        Hashim Khan

        Comment


        • #5
          Perhaps it's aluminum!

          Edit:
          ..........and the machines were new.
          Last edited by Glenn Wegman; 07-16-2009, 10:55 AM.

          Comment


          • #6
            Originally posted by J Tiers

            .................................................. ....................

            I mean cuts like that on a 9 or 10 inch SB, Logan, Atlas, etc, the same kind of deal as the old texts.....
            But, what were they cutting?

            Steels tended to be softer, freer cutting back in the day. I have cold rolled mild steel, 1018, purchased 30 years ago, no comparison to what we get these days.

            Talk with some old timers in the screw machine industry about the quality of material available today.

            BTW, usually when you complain about low quality steel these days someone will pipe in about it being low quality import material. Wrong... It's made in good old USA.

            Comment


            • #7
              A quick look in the chip pan of my SB9 reveals a good selection of almost entirely ferrous chips from the last two days. Many are from large diameter drilling but a good number are from turning including some .050 DOC roughing passes taken in 1040 medium carbon steel in high back gear. The really fine chips are from hard turning high RC treated steels with unobtainium inserts with imaginary rake angles.

              Free software for calculating bolt circles and similar: Click Here

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              • #8
                Originally posted by J Tiers
                Some of those old textbook pictures show small lathes using lantern posts taking off a D.O.C. of what looks like 0.25" or better. You know, the picture with a large coiled single-piece chip coming off the part, and a real whopper of a diameter reduction. The chip does not look like it is a thin ribbon, either, it looks pretty substantial, at least several thou thick.
                Right, and those chips are always shown on museum piece South Bends, Clausings, Logans, ... where every surface has been lovingly scraped to 40 points per inch, and the toolpost has been expertly flaked by a master engraver. How come my lathe didn't come like that?

                Have any of you ever duplicated that sort of performance?
                The problem with questions like that Jerry is that it always turns into a "Ah caught a fish this big" free-for-all. The last time someone was complaining about the 7x10 mini-lathe, a guy replied back that he makes his living on a 7x10, and he takes .050" DOC on stainless steel.
                "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

                Comment


                • #9
                  Originally posted by Glenn Wegman
                  Perhaps it's aluminum!

                  Edit:
                  ..........and the machines were new.
                  ...........and there was no internet with nay-sayers telling them that they shouldn't make cuts like that. LOL.

                  .

                  Comment


                  • #10
                    That could have something to do with it :-)

                    I know I make cuts on my little minimill that I keep reading, both here and on the yahoo minimill group, shouldn't be done. I work mostly in 6061, but burying a 3/8 roughing mill full width and half depth is something I do pretty regularly.
                    Vibrates the living hell out of everything around it, but it removes metal very quickly. I don't get a lot of time to play with my mill, so I try to do as much as I can with the time I have.

                    When I use the mill as a lathe and chuck up a piece of steel (though I use 12L14 cause it's easier), blue chips go flying.

                    My philosophy has always been it only cost $400. Push it til it breaks then repair it.

                    Originally posted by gnm109
                    ...........and there was no internet with nay-sayers telling them that they shouldn't make cuts like that. LOL.

                    .

                    Comment


                    • #11
                      Originally posted by gnm109
                      ...........and there was no internet with nay-sayers telling them that they shouldn't make cuts like that. LOL.
                      Well, the flip-side is also true: everything/everyone is bigger, better, and smarter on the Internet than in real life
                      "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

                      Comment


                      • #12
                        I think Fasttrack may be on to something. I believe that his experience with better tool life taking a larger depth of cut rather than a smaller one has some physics behind it.

                        I believe that the physics involved in the high depth of cut being easier on cutters is a phenomenon called adiabatic shear banding. In adiabatic shear banding, a very localized stress applied to the metal is intense enough to cause local heating so great that softening occurs. Failure (where the chip leaves the stock) thus occurs in a very thin region which has been heated to the point of softening by physical forces while the remaining material farther from the cut is still at normal hardness.

                        In short: ASB occurs when the energy deposited by the action of cutting forces accumulates much much faster than thermal conductivity can remove it from the point of failure. The intense mechanical heating with no loss mechanism on a small timescale causes even very hard materials to soften locally and in the machine tool sense cut at a lower than expected force.

                        ASB also is a dreaded failure mechanism in certain kinds of ballistic armor.

                        Regards,

                        Cameron

                        Comment


                        • #13
                          After the "carbide wars",
                          in the task of selecting the right tool for the job, there is no war, just shades of ignorance

                          Originally posted by J Tiers
                          ....and other discussins of lathe capabilities, it occurred to me that the old-timers seemed to have done much better than we do, despite our high-falutin' exotic grades of carbo-stellite-unobtanium with poso-negatory rake etc.

                          I often take a pretty deep cut when using the lathe, finding that it produces less bending on the part if the tool is ground right.

                          But....

                          Some of those old textbook pictures show small lathes using lantern posts taking off a D.O.C. of what looks like 0.25" or better. You know, the picture with a large coiled single-piece chip coming off the part, and a real whopper of a diameter reduction. The chip does not look like it is a thin ribbon, either, it looks pretty substantial, at least several thou thick.




                          Your comment mentions the lack of modern cutters and DOC but not removal rates....old fashion hss or even carbon steel holds an advantage in DOC. Carbide's stays hard at higher temperatures; temp is a function (mostly) of cutting speed so carbide lets you do is spin faster producing higher removal rates. However with depth of cut the constraint (outside of machine and work rigidity) is spindle HP. As the nature of the cutter material allows a more acute cutting edge on hss, this in turn results in a short shear plane infront of the tool. The shorter shear plane, the wider it can be (for a given HP), ergo you should be able to get more DOC with HSS than carbide.

                          This is hardly promoting hss over carbide for production where matters is removal rate, however it does explain why the old pics can show a great big depth of cut without the benefit of modern cutter materials
                          .

                          Comment


                          • #14
                            This certainly doesn't relate to a Logan or SB but it does relate to a large DOC.

                            I started work in a shop on 1-13-67 and was told about turning a bad soft cast iron roll off a shaft. The roll was about 3' to 4' dia and about 8' long. The shaft was 12" dia and still in good shape. They didn't want to press the shaft out for fear of bending it. So the decision was made to machine it off.

                            The lathe was a 48" Huston with a 100 HP DC motor.

                            Three tools were used in a single pass. A gang tool holder was made to hold three tool holders with the second tool 3/4" deeper than the first while the third tool was 3/4" deeper than the second. When the first tool was set for a 3/4" depth of cut, you removed 4-1/2" off the diameter in one pass.

                            This was before my time there so I didn't see this but I don't doubt it. I did run the lathe and I did see the gang tool holder. (The first liar doesn't stand a chance)

                            Jim W.
                            ps; This isn't a lie.

                            Comment


                            • #15
                              So ya got a 9" SB with a 1/2 HP motor or a 48 Betts Bridgeford with a 50 HP faceplate drive? It all means the same thing: getting the economical best you can from what you got. Good tool selection, technique, job planning, ect and making the cut appropiate for the machine, place in the work plan, and the work goes a long ways to ensure uneventful success and good machine durability.

                              You have a lot - a LOT - of factors to consider when undertaiking a job on a machine tool if you are to meet the work requirements, minimizing wear on the machine, and keeping the boss happy. Working the machine as near its cutting capacity when possible actually reduces wear and tear. Its the distance traveld with the ways system that produces wear. A dozen cuts where two would do means 7 times as much unnecessary back and forth. The load on the ways from cutting forces is but a small factor. It can't be all light cuts or heavy roughing cuts. Productive operation means the minimum of either that accomplishes the most effecctive work. Regardless it's a balancing act.

                              A fellow who can make a 1/2 shoulder bolt in a 9" SB with a 1/2 HP motor in an hour is as productive as his counterpart across the shop on a 4 head planer mill hogging inches off big forgings. They both working their machines to capacity. If the machine is running smoothly and the load meter is at or near 100% you really can't do much more.
                              Last edited by Forrest Addy; 07-16-2009, 04:08 PM.

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