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Thread: Acceptable spindle play, Logan 825 10 lathe

  1. #31
    Join Date
    Jun 2018
    Location
    Tucson, AZ.
    Posts
    11

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    Today I have another project to get working on so I probably can’t get to the lathe. I need to finish building my rotary phase converter, I need my mill up and running ASAP. The VFD I was using blew up last week. I’m done with VFD’s.

  2. #32
    Join Date
    Jan 2004
    Location
    Missouri
    Posts
    30,413

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    Out of curiosity, what brand VFD?

    Most of them are pretty robust, and generally they will protect themselves decently. Some are not as good.
    Last edited by J Tiers; 02-11-2019 at 03:23 AM.
    1601

    Keep eye on ball.
    Hashim Khan

  3. #33
    Join Date
    Jan 2004
    Location
    Missouri
    Posts
    30,413

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    OK, this is the equivalent diagram for the OP's lathe headstock, which I am posting for him. So it is very similar to the headstock diagram I posted above, without any preloading spring washers. The spindle depends on the internal preload of the double row bearing for accuracy and stable positioning.



    That really DOES bring it down to the bearing being possibly the wrong one as far as clearance is concerned.

    I would be surprised that the problem never showed up in anything but parting off. BUT..... in my case, I replaced the original bearing with the one I bought from Logan, and did not have a problem until I later replaced the back gear pinion on the pulley, which meant I had to take the spindle out. At that time I cleaned up the thing, so that the rear bearing could slide as intended.

    Turns out that I had apparently put in some inadvertent preload, because after the cleanup, the lathe chattered like crazy. I had to invent and install a scheme to preload the high-clearance bearing, replacing my "inadvertent preload" with 90 lb of preload from belleville spring washers. That took care of the issue and I can now part off easily. But, of course it is not "right", the bearing should have been the zero clearance type, but the folks at Logan were not aware of that then. I can hardly blame them, the machine was 60 years old at the time, and the present owner and workers were not even born when it was made.

    Anyhow, If I could have a situation hide the loose clearance bearing for several years, I can hardly be surprised if the OP has not noticed his loose clearance bearing except for during part-off.

    I think the next action is going to have to be pulling the spindle and having a good look at the bearing to see if it really IS that loose, or if there could be any feature of the headstock casting that is allowing the movement.

    If that one spring washer is not present, that will need to be put in place, anyway, to ensure the nose bearing is held stable axially. after that, a good look at the casting, and checking the bearing.
    Last edited by J Tiers; 02-11-2019 at 03:42 AM.
    1601

    Keep eye on ball.
    Hashim Khan

  4. #34
    Join Date
    Jun 2018
    Location
    Tucson, AZ.
    Posts
    11

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    The VFD is a WEG, made in Brazil. Pretty decent quality. This issue was my fault, I allowed a chip to drop down inside the cooling vent slots for the circuit boards, or maybe that I was running right close to the maximum rated amps. I didn’t buy the VFD to power this mill, it was to be used when I repowerd my Hardinge mill from 1 hp DC to 1 hp 3 ph. So the VFD was a bit on the smaller size, rated for 2 hp and my Kent mill is either 2 or 3 hp. The motor tag is missing and they came with either motor. I have been using this VFD on this mill for about 3 months.

    But VFD’s are another subject all together and I want to keep this thread on topic!

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