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Gota question for ya'll about a lathe

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  • Gota question for ya'll about a lathe

    what kinda lathe has a 120 graduation dial on the cross slide and why????

  • #2
    Because the crossfeed screw has a pitch that has .120" per revelution. Several brands have 120 divisions on the dial. Why they chose that I don't know.
    It's only ink and paper


    • #3
      I bought my first Taiwanese lathe from a friend. The cross slide and compound had regular graduations, but I noticed that the carriage handwheel was graduated a bit unusually, and engraved on it was a notice that each division = .006"

      I asked my friend why that was, and he replied, "because they hate us, of course."

      Frank Ford


      • #4
        120 is simply the highest number on the dial. The other five marks back to zero makes for 125, or 0.125"- an eighth-inch per turn.

        That's a pretty fine thread, but nothing particularly unusual.


        [edit] Or I might be wrong on that one.
        Doc's Machine. (Probably not what you expect.)


        • #5
          so for each mark on the dial how many thou does it take off the dimeter of the bar then,,,


          • #6
            depends on whether it is a radius or diameter dial. I'm guessing its radius, but I don't know.

            Either way, the best way to figure this out is to try it. Take a cut with a depth of say 5 graduations and measure the change in diameter of the part. Divide that change by five and you have your answer.


            • #7
              Apparently some older machines were graduated that way, but with a small difference.......

              They were marked with US graduations, but actually moved a different distance, in even mm. You might want to be certain that you know the actual movement distance.

              Keep eye on ball.
              Hashim Khan


              • #8
                this one is on a standard moderen 9x20 lathe


                • #9
                  Attach a dial indicator to the tool post. Put the other end against work held in the chuck crank the cross slide and you can see what the graduations do.



                  • #10

                    3.0mm/25.4in = 0.1181" ~ 0.120"

                    or ((0.120 - 0.118)/0.120) = (0.002/0.120) = (0.0167 x 100 = 1.67%).

                    My guess is that it is a 3.00mm pitch thread which has a lead of 3.00mm ~ 0.118" and the dial is divided in 120 parts. The error is 1.67% which may be negligible if you are only moving in say 0.010" ("ten thou") x 0.0167 ~ 0.0002" ("two tenths").

                    If the cross-slide is a metric pitch then so might the top-slice and the main lead-screw be.


                    • #11
                      I have the Standard Modern 1120 lathe. It has a cross feed dial with 125 graduations on it, as it has an 8tpi thread. Moving the dial by one division takes 0.002" off the diameter of a part.

                      I guess they figured that a 10 tpi thread (therefore 100 graduations of 0.001" on the dial) would be too fragile but I am surprised that the 920 has the coarser thread.



                      • #12
                        Doc probably has it, the graduations probably are for 125 counts. The lead screw is either 8 or 16 TPI depending on the setup of the lathe.

                        The simplest solution is to take a clean up cut and then take a light cut, say 5 divisions and measure the amount the workpiece has been reduced.

                        Standard Modern is a Canadian manufacturer, and the lathe is probably Imperial. Some of the low end Chicom imports use a mix of Imperial and metric lead screws and handwheel graduations that have little or no relation to any real world measurement, but I doubt SM is guilty of that.
                        Jim H.


                        • #13
                          Seen that mixup of imperial and metric on a machine a couple weeks ago. What pile of crap that is. I'm surprised more people haven't piped up about this, actually.
                          I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-