Thanks to all the helpful hints.

wrote in message
ups.com...

Douglas Adams wrote:
We just had new ballscrews installed on our knee mill and are finding
a
slight "vibration" or chatter while manually indexing the screw on
the
x-axis. You can feel it occurring around the same position i.e.
between 0
and 90 degrees rotation of the screw.

Their doesn't appear to be any interference issues between the screw
and the
frame.

Any suggestions on trouble shooting this one?

The installer is being dodgy on addressing this issue.


Perhaps the ballnut isn't exactly lined up with the end bearings. You
get a ballscrew trying to work on two different axes at the same time,
and it sometimes finds a way to let you know things are off. Is there
a movable bearing holder/pillow block of some sort on either end? If
so, see what happens when you unbolt it. If the screw pushes the
bearing block to the side or anywhere else, things aren't lined up
properly. What does the block do if you turn the screw while it's
loose?
Another thing that just went through my mind would be to find a way
to check pitch diameter at various angles of rotation. Things might
not be as concentric as people assume. Happy hunting.

Later,

Charlie