What’s an acceptable taper for a lathe

  1. R-D-R Forum Supporter

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    E2591E98-AB71-4953-B4E7-904C8B3ADCDA.jpeg My lathes been to bits a few times this past month for various reasons. It’s all back together and running well, given I shuffled it around a bit I checked and I seemed to have a bit of taper action going on.

    I properly levelled the ways at both ends using a machinist level and made a test bar up. Tweaked the front tailstock leg I now have a 0.003mm taper over 150mm the larger end being near the headstock. This was on 40mm steel with .002mm cuts.

    I wasted an hour trying to get it better but seemed to be travelling down a long dark rabbit hole.


    What’s the thoughts shall I call this good?
     
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  2. eLuSiVeMiTe

    eLuSiVeMiTe Forum Supporter

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    For me that's fine. Depends what your making I suppose.way less than a thou.
     
  3. graffian

    graffian Seer unto the end of his beard

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    Just over a tenth?
    I woudl love to have that little taper, what is it if you turn something small diam?
     
  4. Maker

    Maker nEw mEmBeR

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    What's the lathe? The headstock can be moved relative to the bed on some lathes to sort this.

    Acceptable depends on the work you're doing, I'd be happy with less than a tenth taper over 6 inches though.
     
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  5. citizen kane Member

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    UK Hampshire
    Are you sure the decimal point is in the right place, I would be surprised if you could take a 2 micron cut with a tipped tool, doesn't it just rub?
     
  6. grim_d

    grim_d Forum Supporter

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    Is your decimal point in the right place?

    I absolutely wouldn't be worrying about 3 microns. I don't even have a mic capable of reading to that

    I would think the variation in surface finish might be as much as 3 microns!
     
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  7. R-D-R Forum Supporter

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    Yep it’s defo 0.003 measuring it with a mitutoyo digital micrometer and achieved same result over 4 consecutive cuts.
     
  8. Hood

    Hood Forum Supporter

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    Use a normal analogue mic and your lathe will be spot on with no taper ;)
     
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  9. Hood

    Hood Forum Supporter

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    Depends on the insert, a decent quality one with a small nose rad and a sharp and positive profile will easily do that.
    The one in the pic however does not look like one so yes it will not be cutting at its best, it will still cut though but ..
     
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  10. R-D-R Forum Supporter

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    Just re read the cut was 0.2mm not 0.02. I set it using the dro then locked the slide off to avoid it moving due to backlash.
     
  11. Hopefuldave Intergalactic pot-mender

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    If it cost you less than £50k, it's well within spec...
    Schlesinger's book on inspection puts taper per 300mm at 0.008 near the chuck, 0.015 at 300mm from the chuck - for "Toolroom Lathes (Highest Degree of Accuracy)" up to 200mm centre height - you're doing well!

    Dave H. (the other one)
     
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  12. R-D-R Forum Supporter

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    Harrison m250 I bought it for £380 and restored it.

    I think I’ll call it good then :laughing:
     
  13. slim_boy_fat

    slim_boy_fat Forum Supporter

    As can the tailstock setting, easy and less chance of mucking with the headstock factory setup. ;)
     
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  14. Shox Dr

    Shox Dr Chief Engineer to Carlos Fandango

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    I think we need ‘smug pipe smoking dog’ emoji Oooooooh yessssss:laughing:
     
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  15. Hood

    Hood Forum Supporter

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    The thing is, the tailstock can only be aligned with the spindle and the spindle first needs to be aligned with the bed.
     
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  16. R-D-R Forum Supporter

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    I also aligned the tailstock this afternoon too. Centred it and made sure it’s true to the ways on the assumption the headstock is.

    I haven’t messed with the headstock not even when I restored it I think it’s as it was when it left the factory.

    checked the spindle bearing as per the instructions that’s within spec too.
     
  17. Pete.

    Pete. Member

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    Nope you should call it done. Five times that would have been good.

    Now part that piece off, face and centre-drill it both ends and put it between solid centres and do the same test. Adjust the tailstock until it turns the same both ends.
     
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  18. R-D-R Forum Supporter

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    Pete thanks for that I will try it tomorrow it’s a much better way of doing it.
     
  19. grim_d

    grim_d Forum Supporter

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    I'd say that's likely better than when it left the factory then.

    That's a well set up machine.

    I'm actually amazed that a used machine, even a little used machine,will do that well so close to the chuck.
     
  20. eLuSiVeMiTe

    eLuSiVeMiTe Forum Supporter

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    Been meaning to do some tests on mine for over a year. Never seems important when I get some garage time.
     
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