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Turning a part with shoulders at each end?

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  • Turning a part with shoulders at each end?

    Hi folks,

    I'm pretty new to operating a lathe and this weekend had to turn a part with a shoulder at each end, where the gap between shoulders was only about 35mm long, and the height of the flange/shoulder was about 8mm (35mm large diameter, 27mm small diameter).

    I thought about different ways of doing this and briefly experimented with plunging a RH turning tool into the workpiece, but given the small space available and the large depth of the shoulder it was obvious this was going to be a right faff on - Awkwardly plunging the tool and trying to turn to diameter then switching to a LH tool and repeating? Especially as my turning tool has a good 10-12mm wide tip, it barely fitted into the gap.

    In the end I turned the piece without the shoulder on one side then made a push-fit one... But this took a while.

    Just wondering how this would normally be solved, should I have made two recesses with a parting tool and then ground a 'thin' turning tool? Could I have ground a tool which could turn both ways?

    The lathe is an 8x14 mini thing.

    Cheers for any advice.

  • #2
    You did not state what material. Me... I'd Use a parting tool... or grind some HSS into a grooving tool.

    I'm sure others will be along shortly to give their view.
    Wow... where did the time go. I could of swore I was only out there for an hour.


    • #3
      If you wish to insure concentricity of all diameters you center drill both ends and turn between centers switching ends to do the other diameter. You need a lathe dog, either manufactured or home made. Sounds like you need to do some reading as this is one of the old time basc methods. Peter
      The difficult done right away. the impossible takes a little time.


      • #4
        I made a tool that does right and left hand cutting at once

        Its basicly just a wide (1/4") parting like tool, Except the tip has a gap in the center to massively reduce cutting tip contact.

        Sorta like a snake toung. You can only make passes as deep as the gap in the center, else the entire tip contacts at once and it chatters. But you can plunge in a little bit and turn in either direction, right up to shoulders, then plunge in some more and turn back.
        Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.


        • #5
          I ground this years ago for a special job we were doing at work. It may work for what you did if the depth was not to great but I prefer a larger tool. for what you were doing.

          I have used it at work and at home many times. 35mm=1.377" wide so an ordinary cutter up to 1/2" should have done the job. Sometimes I plunge cut with a 60 deg cutter to within .010" of depth by plunging and moving the cutter side to side. Then I finish up with the 60 deg cutter angled toward each side to finish one side and then the other side. For your groove you may had to use a left and right hand cutter to do it after the V nose cutter.
          It's only ink and paper


          • #6
            I kind of agree with Carld, If you use a right hand tool and plunge in 0.010" - 0.020" at a time you can rough out some space to work pretty quickly. You probably want to leave 0.050" or 0.100" on the dimensions while you are hogging out the material, and then once the majority is excavated go in with the left and right hand tools to clean up each side.

            Othat than that, the double side tool looks pretty cool. Who can argue with a tool that looks like a serpent tongue?


            • #7
              I would have roughed it out with conventional tools and finished with a grooving tool (my parting tool is ground with an angled front face, whereas the grooving tool is square). I really like the idea from a couple of members of grinding out the front face. Clearly if you plunge with it the design is no better than if it had simply left square, but for finishing passes I can imagine it would work well, and with less deflection than a grooving/parting tool when traversing.



              • #8
                Yes, rough it out with left and right hand tools and use a parting tool or one of the above ones to finish it. Plunge in on one shoulder, go across to the other one and then back out.

                For maximum accuracy, leave at least 0.010" for the finish cut and do it in two steps. Do one to take off about 0.005" and then measure. Then do the final with due adjustments on all three surfaces. Since you are only taking shallow cuts with the final tool, it can be narrow enough to fit in almost any space between the shoulders.

                I have also done this to make circular groves in a face when making a back plate for a chuck. But the "parting tool" used for finishing must have extra clearance on the outer (left hand) edge to clear the inside radius being formed.
                Paul A.

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