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  • Out of level lathe;unintentional taper

    Hey guys,

    I know the following question has a great many vairables but I need to seek wisdom from the experienced.

    I have moved to a different location. My lathe is still on it's shipping pad. It is not level nor have I attempted to make it level. I am waiting for the concrete pad to be poured before taking it off the shipping pad and setting the lathe in its final resting place. I have turned a couple of very short pieces (~1.5" long X 1.25" dia with the lathe sitting on the shipping pad). Turning took place with the work piece sticking from the chuck's jaws by approximately 1.75". I did not use the tail-stock. I was basically doing a "tickling cut" to slightly reduce the diameter by only several thousandths.

    I ended up cutting an unintentional taper. Can't remember which way the taper ran. There was about .002" difference over all length (approx distance 1.5").

    Can this much taper, over such a short distance, result if the lathe is not level or is it more likely that I have somehow managed to cause the head to become misaligned during shipment?

    Harold
    For those having fought for it, Freedom has a flavor the protected will never know.
    Freedom is only one generation away from extinction.

  • #2
    At the risk of being hung, drawn & quartered here, I'd say that having a lathe level or not has no effect on how it cuts or whether it turns taper. Lathes are found on ships, and they seem to do fine.

    What's more important is if the lathe is sitting on uneven ground, such that the bed twists (assuming the lathe has 4 feet on the ground as most do, not 3).

    A bit of shimming under the feet might sort the problem out.

    Ian
    All of the gear, no idea...

    Comment


    • #3
      At the risk of being hung, drawn & quartered here, I'd say that having a lathe level or not has no effect on how it cuts or whether it turns taper. Lathes are found on ships, and they seem to do fine.
      I won't pitch and tar you!
      But "leveling a lathe" means something different. It means by most to get the twist out of the bed (with the help of a level).
      But I doubt that any bed can have that much twist to get the numbers posted.


      Nick

      Comment


      • #4
        Originally posted by MuellerNick
        I won't pitch and tar you!
        But "leveling a lathe" means something different. It means by most to get the twist out of the bed (with the help of a level).
        But I doubt that any bed can have that much twist to get the numbers posted.


        Nick
        So are we saying that the head may be out of alignment? Keep in mind that the lathe is bolted to a wooden shipping pallet and the "legs" are not touching the ground.

        Harold
        For those having fought for it, Freedom has a flavor the protected will never know.
        Freedom is only one generation away from extinction.

        Comment


        • #5
          Well, for the stickout and diameter, I don't expect that much deflection. But before paniking, I'd accept it for now, and level the lathe ASAP.

          No further guessing, mix the concrete!
          Nick

          Comment


          • #6
            Originally posted by hwingo
            Keep in mind that the lathe is bolted to a wooden shipping pallet.
            That could well be the problem.

            You haven't told us what kind of machine this it. Many of the smaller lathes, even something like a Myford can have considerable stress 'put in' to the bed if bolted down unevenly.
            Paul Compton
            www.morini-mania.co.uk
            http://www.youtube.com/user/EVguru

            Comment


            • #7
              Harold, you stated you did not use the tailstock. Could your chinese chuck be not perfect? Also, after a good level and set up remember that the tail stock has a side to side adjustment too. That can remove a taper problem.sometimes. JIM
              jim

              Comment


              • #8
                Tweaking

                Harold.

                "Leveling" is bit of a misnomer.

                All that is theoretically required for the lathe so be as it was when it was manufactured - assuming no or minimal wear or distortion - is for the lathe bed to be "flat" and that all important parts to be co-planar.

                It just so happens that if that plane in which all that stuff is horizontal it makes it easier to check, and if necessary to correct with a good level until all those points are in a horizontal plane.

                If the lathe was tilted say 5 degrees and all points were co-planar, it would probably work just as well as if it were horizontal - but it would be lots harder to measure - although it can be done with a very good inclinometer.

                "Starrett" 199 "master levels" - or equivalent are the usual levels of choice for this sort of work.

                After the lathe (bed) is set level the alignment of the head-stock may be next and after that some test cuts. If the test cuts are not satisfactory as regards taper etc. the lathe bed may be "tweaked" by twisting it by adjusting the leveling screws that fasten the lathe to the floor/slab/bench.

                It can be very frustrating and often counter-intuitive.

                But that's life.

                Wait until you have set the lathe level on what-ever it is mounted on - slab or bench etc. - and see if there is any real adjustment really required.

                Comment


                • #9
                  Originally posted by EVguru
                  That could well be the problem.

                  You haven't told us what kind of machine this it. Many of the smaller lathes, even something like a Myford can have considerable stress 'put in' to the bed if bolted down unevenly.
                  Originally posted by jimmstruk
                  Harold, you stated you did not use the tailstock. Could your chinese chuck be not perfect? Also, after a good level and set up remember that the tail stock has a side to side adjustment too. That can remove a taper problem.sometimes. JIM
                  EVguru: The lathe is a PM12X36.

                  Jim: Naturally it's possible the chuck is off. That having been said, the chuck I am using is a 8" Bison 6-jaw chuck. The chuck is new (perhaps 8 to 10 total hours of use).

                  Good Morning Tiffie and others having responded. I suppose that I will be able to realize more when the lathe is properly set. I just couldn't imagine such a short piece having so much disparity that close to the chuck. If the piece were 12" inches with the end free of support then I could wrap my head around "cause & effect".

                  Harold
                  For those having fought for it, Freedom has a flavor the protected will never know.
                  Freedom is only one generation away from extinction.

                  Comment


                  • #10
                    One needs a really bad juck to get some taper. If the jaws' gripping faces are really conical, then it's doable.


                    Nick

                    Comment


                    • #11
                      hwingo, once you level it up and set the headstock your lathe will cut true.

                      In answer to your original question, yes, being even slightly out of level, you will cut a taper.

                      I too, have moved, and with building the shop and doing the million things one does when moving, I never gave the lathe much attention.

                      One a recent job, after having days (literally) of frustration cutting unintentional tapers, I went back and reset the headstock, taking hours of time. Everything good.

                      One day I checked the level at the tailstock end, and had to tweak it a bit.

                      Guess what! Now lathe was cutting tapers again! So I had to re-level both ends, and realign the headstock again.

                      Ok, now things are great, but I was one of those that for decades believed "level" was not a critical thing. Now I know that even a quarter of a turn on a leveling bolt will cause tapers.

                      #1 on my machine tooling "to buy" list is a decent level.

                      Comment


                      • #12
                        Question is the tailstock lining up with the headstock? maybe the tailstock is needing tweaking a little to centre it. Alistair
                        Please excuse my typing as I have a form of parkinsons disease

                        Comment


                        • #13
                          Originally posted by jimmstruk
                          Could your chinese chuck be not perfect? JIM
                          How would the chuck have anything to do with the workpiece having a taper? If it had been a Bulgarian chuck it would have made no difference.

                          Comment


                          • #14
                            If the chuck is not mounted (or machined) square to the spindle, it will move the workpiece in an arc that increase with distance from the chuck, and that cuts a taper that gets smaller towards the tailstock.


                            One of my lathes cuts a taper that INCREASES in diameter as you proceed from the chuck - and it's not work-piece deflection... that needs to be tracked down, but can't take the lathe out of service right now..
                            Last edited by lakeside53; 06-16-2010, 12:22 PM.

                            Comment


                            • #15
                              Originally posted by lakeside53
                              If the chuck is not mounted (or machined) square to the spindle, it will move the workpiece in an arc that increase with distance from the chuck, and that cuts a taper that gets smaller towards the tailstock
                              No, it doesn't.

                              If the cutting tool is moved parallel to the axis of rotation then you end up with a parallel cut. The chuck being off centre or off square just means the axis of rotation wouldn't be down the centre of a round bar.
                              Paul Compton
                              www.morini-mania.co.uk
                              http://www.youtube.com/user/EVguru

                              Comment

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