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Used Lathe Runout?

Discussion in 'Newbie' started by Dan Bevilacqua, Nov 15, 2017.

  1. odie

    odie

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    I was able to check the runout of my spindle earlier this afternoon. As you can see, there really isn't a good place to set the dial indicator on the exterior of the spindle.
    IMG_3358.JPG
    .....so, I was able to get a good angle on the interior of the Morse Taper. This doesn't necessarily mean I'm getting a good indication of the exterior of the spindle, but it's probably pretty close. Here I was getting about .00075", or about 3/4 of a thousandth of an inch runout.
    IMG_3359.JPG
    I then installed a 1 3/4" SC faceplate, and took a measurement of the outside surface. Here, I was getting about .00175", or about 1 3/4 thousandths of an inch runout. This measurement probably includes some amount of error in the integrity of the faceplate.
    IMG_3360.JPG
    -----odie-----
     
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  2. Bill Boehme

    Bill Boehme Administrator Staff Member

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    Well, I suppose that's good enough for cutting wood. :D :rolleyes: :p

    When you take the reading off a faceplate or spur drive or anything attached to the spindle then we can't really say what the measurements mean other than it's more than satisfactory, especially with the measurements that you got even with the faceplate

    The wood is going to distort a lot more than that once it has been finished and and sitting on a shelf for a while.
     
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  3. john lucas

    john lucas

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    I just checked my two lathes. A Delta Midi and a Powermatic 3520A. Checking inside the morse taper like Odie showed I had zero runout on either lathe. I checked the face of the spindle which is also a critical alignment and no runout there either. I have checked other lathes and found as much as .003" but didn't have any complaints from the user on those lathes.
     
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  4. Leo Van Der Loo

    Leo Van Der Loo

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    My large lathe has tapered roller bearings running in an oil bath, there is less deflection on that lathe than on my two smaller lathes that use ball bearings, the distance between the bearings does also affect the amound of vibration because of required clearances in the ball bearings, this is usually also not measured when rotating a spindle, as the weight will keep the spindle down, but when turning the spindle wil be lifted up and can give you vibration.

    As to the OP’s question, I would think a total runout below 3 thou would be acceptable to me, less is better of course, though there is always some, even the grinding marks will give you some, especially in the fairly coarse machining that we normally find on the low cost far east machinery.
     
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  5. Bill Boehme

    Bill Boehme Administrator Staff Member

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    I just checked my lathes with my most accurate wooden yardstick and didn't detect any runout.
     
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  6. Dan Bevilacqua

    Dan Bevilacqua

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    I appreciate all the information. It should come in handy if I run across a good deal on a used lathe. I'll bring my dial indicator.
     
  7. odie

    odie

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    Since I do have some amount of runout, even though very small......I wonder if the reason for that is in the manufacturing, a horrendous catch, or worn bearings. What else could be the case? For my Woodfast, the bearings were replaced last year, and my worst catches were on the first two lathes I owned. By the time I owned the Woodfast, I had been turning for about 10 years, and the really big catches I had early on were already past tense. So.....I suspect the spindle was originally manufactured with some amount of runout. It was made when most industrial manufacturers were making a transition to CNC machining.

    Although, I was not involved in CNC production myself, I did work in a machine shop during the time it made the transition. My opinion about that, is CNC is capable of precision machining, if the program is made by a competent computer programmer, and sharp tools are maintained. On the other hand machinery made prior to CNC machinery is also capable of the same precision, BUT competent machinists are much harder to come by than competent computer programmers.

    Anyway, I suspect the error is in the machining of my Woodfast spindle. Does it matter? As others have indicated, it doesn't matter, when discussing wood turning.....(Well, up to a point!) We all want things to be as mechanically perfect as possible, and in the real world, they seldom are. Things that do add to the accuracy of the finished wood turning, are a minimum of remounts. This thinking is basically why I've chosen to use waste blocks for the finish turning. Once installed, the faceplate is never removed, until everything is completed, and finish applied.......except for removing it and turning the foot. In my particular case, <.002" runout has never been problematic. Now, If I were using a chuck for the finish turning, and multiple remounts are in the picture......that will have a considerable effect on how well the details look to the observer.

    Note: I do use a chuck for roughing unseasoned bowls.

    -----odie-----
     
    Last edited: Nov 19, 2017
  8. Leo Van Der Loo

    Leo Van Der Loo

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    You point out a common reason for inaccurate machining Odie, it is remounting a piece, the best way to get everything right is when the whole machining is done without remounting.

    Mind you I have no experience with the newer ways of manufacturing and machining, but that was always the case, and of course cost of tools etc will have the tools used longer and of lower quality, things like that add up as is my experience, and I assume profit is still the main reason things get done or not ;)
     
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  9. odie

    odie

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    Ya.....all true, Leo. :D

    Remounts.....that is a key element to precise machining, and to a degree it does apply to woodturning. It will depend on what level of details are desired. Many turners depend on embellishment done off the lathe, and turn simple, easily sanded shapes for the basis. Nothing wrong with that, and great embellishment is very artistic and admired......but, if the intent is to do detail work on the lathe, the only thing that will support that, is doing everything one can to maintain geometric integrity of the work-piece.......and sanding destroys geometric perfection.....especially in bowl turning, where the grain alternates between long grain and end grain. If one depends on less precision cutting, and more sanding, then the ability to include multiple turned details becomes a smaller option. :(

    ---------------------------------------

    In the industrial world, profit vs quality is a balancing act that sometimes didn't always work out in the best interests of the consumer. CNC machines would often run 24/7 and without an operator. The operator was basically someone who mic'd parts and changed out cutting tools when specs weren't within tolerance. Leaving a CNC machine running unattended is a practice that was strictly profit motivated.....but, the machine itself didn't know when to stop if parts were not in spec. Although modern carbide tooling lasts many thousands of cycles, some do last longer than others! :eek:

    -----odie-----
     
    Last edited: Nov 20, 2017
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  10. Dan Bevilacqua

    Dan Bevilacqua

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    Anyone know whether there is an "industry standard" spindle "runout" tolerance, and if so, what is it?
     
  11. Bill Boehme

    Bill Boehme Administrator Staff Member

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    That would be a manufacturer's performance spec on metal turning lathes. I never heard of that ever mentioned for any wood turning lathe. The amount of runout typically measured is far less than the elastic and plastic deformations of wood as it is spinning on a lathe.
     
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  12. Mike Johnson

    Mike Johnson

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    A runout standard like that would have to be based on the parts that need to be manufactured
    on the machine. Plus or Minus accuracy moving to the right of the decimal point adds to the dollars
    adding up to the left of the decimal point.
     
  13. Hy Tran

    Hy Tran

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    Short answer: No.

    Long answer (don't bother reading if you're not interested):

    Your various machine tool manufacturers are playing trade-off:
    • Satisfying customer needs (whether real or perceived)
    • Making sufficient profit (cost to design/develop/manufacture/support vs lifetime profit)
    • Strategic positioning (compare, say, Thompson tools vs Benjamin's Best)
    ASME B89.1.5 and B89.1.6 (plug gages and ring gages, but I may have these backwards) describe tolerance classes for round objects, typically used in mastering the output of precision machine tools--but since these standards were originally written, there has been a lot of evolution in understanding uncertainty in measurements and in risks. No one makes "triple-X" gages anymore--because they really can't be economically certified when accounting for measurement uncertainty.

    The ASME machine tool stds, B5.54 for machining centers and B5.57 for turning centers describe performance evaluation methods. Note that these are called "performance evaluation methods". They don't give tolerance classes. Not speaking either for industry or for ASME, but rather as an opinionated person: Industry really does not want to set standards for spindle runout (btw, please call it error motion)--what they want to do is to establish maximum permissible error in machine tools, of which spindle runout is only one aspect. Considering the system as a whole, you can trade more runout for higher stiffness, damping, and durability, and have a machine that's a speed demon.

    B5.54 and B5.57 were written by committees comprising academic researchers, scientists and engineers working in the government sector, folks from NIST (actually, probably NBS at the time, National Bureau of Stds), machine tool manufacturers, and end-users, such as aerospace and automotive manufacturers.
     
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