Watchmaker lathe help

Discussion in 'Tips and Tricks' started by kadora, Apr 30, 2018.

  1. Apr 30, 2018 #1

    kadora

    kadora

    kadora

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    Hello Friends
    I have bought this miniature lathe on local fly market.
    I could not resist to buy this little beauty //I can cover it with man handkerchief//.
    I did some negligible de rustings and attached new motor with
    speed controller because original speed regulator is death.
    During refurbishment I have found that offset of main spindle
    is 0.03 mm.
    IS THERE A POSSIBILITY TO IMPROVE THIS OFFSET TO
    HIGHER PRECISION ?
    Thank you guys for your advice.

    2018-04-30-2812.jpg
     
  2. May 1, 2018 #2

    bazmak

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    what do you mean by offset ? A better description with more accurate dims and photos would help.Do you mean that the spindle runout is 0.03mm or the alignment with the tailstock is out ?
     
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  3. May 1, 2018 #3

    Mechanicboy

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    I has watchmaker Boley lathe. 0,03 mm is not much, you can't improve offset since there is not adjustable parts to improve offset in the watchmaker lathe. It's your skill and handwork who create the product in good quality. The spindle has adjustable bearing to adjust play. Do not run tight on bearing, The spindle must run light without resistant and slack from bearing and use thin oil SAE 20 without acid (some watchmaker use acid free sewing oil) as bearing oil for spindle. Normal working temperature is hand warm. RPM range is often from 1500 and up to 4000/5000 PRM due limitation on the maximal RPM on bearing. Calculate cutting speed to select RPM for material and diameter.
     
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  4. May 1, 2018 #4

    bazmak

    bazmak

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    what do you mean by offset. IE between h,stock and Tailstock ??
    or do you mean spindle runout. As you say 11/2 thou is acceptable
     
  5. May 1, 2018 #5

    kadora

    kadora

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    I mean spindle runout offset.
    Thank you guys for your effort to help me
    I am happy to be a member of such friendly and helpful group of people.
     
  6. May 1, 2018 #6

    Mechanicboy

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    Keep clean and free from dust and swarf inside the hollow spindle and collets to minimal offset.
     
  7. May 1, 2018 #7

    goldstar31

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    As 0.03mm is a midge's whisker over one 'real' thousand of an inch, at what distance did you take the reading-- and with what-- and what was its tolerance, please?

    Norm
     
  8. May 1, 2018 #8

    kadora

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    Mechanicboy I have cleaned inner surface of spindle
    still 0.03 mm runout offset.
    goldstar31 sending picture of how i measure offset.
    In the collet is piece of 4 mm linear bearing shaft.
    Thank you

    2018-05-01-2814.jpg
     
  9. May 1, 2018 #9

    DJP

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    Can you measure run out of the main shaft with collet removed? I had similar problems with a three jaw chuck that was worn at the scroll. I marked the workpiece so that it could be returned to the same position within the jaws far a work around until I purchased a new chuck. Chasing a runout problem was frustrating and proving that the main shaft and bearings are OK was the best test. The size of the workpiece also had an affect on run out amount so testing with a larger collet would also be of benefit, in my opinion.

    Maybe a new set of collets for the worn sizes is all that you need.
     
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  10. May 1, 2018 #10

    goldstar31

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    I agree with DJP. The test is NOT usual. I'd have gone for Georg Schlesinger or perhaps Edward Connolly.

    Long time since I read 'Microscope on the Lathe' by Exactus(?) which was probably Ned Westbury. May have been updated since --but !




    Norman


    PC Should be 'Geometer' and if you Google NEME.S ORG it's there.

    We used to be one of the share holders in one of the Tyne's largest machine tool manufacturers . Oddly, I did a restoration article in Model Engineer--- using one of their products.:eek:
    N
     
  11. May 1, 2018 #11

    Mechanicboy

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    Check inside the bore for collet is true. And check the collets with difference diameter and compare with this collet for 4 mm diameter who has offset. If in case this collet is not true, replace with a new collet.
     
  12. May 2, 2018 #12

    Wizard69

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    Welcome Kadora!

    Nice score on that lathe!
    You need to lose that word offset, it just confuses people.

    Spindles have two important and easily measure parameters. One is axial runout. The other is radial runout which is what you are after here.
    The problem here is that unknown parts lead to crappy results when testing for run out. Without a metrology department to test the collet and pin you really don't know what you are measuring. To get around the unreliability of your test set up id look for several collets and arbors to test with. By keeping an eye on spindle orientation you should be able to determine if the spindle is the issue or if the test pieces are the issue.
     
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  13. May 2, 2018 #13

    canadianhorsepower

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    You can sell it to me Ill take it the way it is :thumbup::thumbup::thumbup:
     
  14. May 12, 2018 #14

    GlennS

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    Congratulations on the good deal!

    Are you getting the "offset" reading by ROTATING (spindle runout) the spindle or by PUSH/PULL (bearing play) the spindle?

    Glenn
     
  15. May 13, 2018 #15

    bazmak

    bazmak

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    I now assume you mean spindle concentricity and not alignment with carriage travel ?
     
  16. May 13, 2018 #16

    kadora

    kadora

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    Thank you guys.
    Yes I mean spindle concentricity .
    English is not my mother language so I do often many mistakes .
    By the way what is difference between RUN OUT and CONCENTRICITY ?
    //GOOGLE TRANSLATOR does not serve me in this case//.
    Thank you again .
     
    Last edited: May 13, 2018
  17. May 14, 2018 #17

    Wizard69

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    No problem, we will eventually figure it out. It could be worse i once went on a trip across the state to a supplier and had a bit of communications confusion that left me looking at one of our engineers asking what is he talking about. Supposedly we spoke the same language but local definitions for words collided.
    That is a very very good question and has caused me to think a bit. Due to that thinking i could be completely wrong so consider the explanation below carefully.

    CONCENTRICITY in my mind is a specification relating one feature to another. For example the bore in a shaft with respect to a bearing journal. It is a very specific relationship.

    RADIAL RUN OUT from my perspective is a measurement that can sum up a number of tolerances. So lets say we have a shaft with a bore and bearing journals as above. Those bearings may be roller elements with their own runout at each location on the shaft, the journals will have runout with respect to the bore and that bore might not be perfectly round. All of these factors add up to give you a measured RUN OUT. The run out isnt specific to any one feature, at least not until more detailed measurements are made.

    Another way to look at this is say you have a bad crash on a machine. After the crash you measure significant RUN OUT in the spindles bore. You then need to determine where the issue is, did the bearings get damaged, the spindle bent or the bore deformed? Measuring gross RUN OUT alone might not get you to the root of the problem.

    I hope others respond but this is my perspective on the differences between the two terms. Concentricity is a very specific specification where as run out measures a sum of motions.
     
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