Z Axis Bearings or Encoder gone bad?
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  1. #1
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    Default Z Axis Bearings or Encoder gone bad?

    I have an early 90 model Okuma Cadet LNC-8 lathe. In the middle of running parts I noticed it cut a huge chamfer on the ID of a part. Then one minute it didn’t cut it at all. Then another o-ring groove was cut incorrect in Z.

    I checked backlash in Z and moving one direction with the machine in tenths two clicks on the hand wheel it moved .0002 before my interaprid .0001 indicator would move. Then in the other direction it took 7 clicks with the hand wheel to move .0002. So I wouldn’t think the Z axis bearings were bad. What could I check for regarding the encoder? Or any other suggestions anyone may have.

    Thank you for any help in advance.

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    Seems like the motion you saw was under no load, try applying force to the axis and see if movement increases. Could be a thrust bearing, but what else is in the motion path? Any belts, pulleys, connections that could have loosened?

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    That’s what I was thinking based off other people’s previous experiences being the thrust bearings. I have some on the way along with the bearings at the other end of the ball screw. When I checked my tool data the number changed when I rechecked touching off the face of a part. There isn’t much load cutting 1” diameter aluminum. This pictured shows the big ID chamfer it randomly cut.

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    That looks like a pretty clean cut, which is worrying if it points to a control issue rather than mechanical. I've no experience with your lathe, so hopefully someone else sees this and might have something useful to say.

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