On 1/14/2018 1:25 PM, Bob La Londe wrote:
I'm learning a lot... like you hardly need any torque on the thrust
bearing retaining nut on this KMB1.Â* I learned how to make new tab lock
washers too since nobody stocks them, but several say they can get
them... eventually.Â* I even learned what the X axis is supposed to sound
like with good thrust bearings.Â* It never really had any problems, but
its sure sounds a lot smoother now.Â* Obviously the bearings were bad.

With new thrust bearings on the Y-Axis its pretty smooth now too, but
only for about 7/10 of a turn.Â* Then it pulses.Â* Its actually a lot
worse than it was before.Â* Before I could see a little flutter about
every 1000 steps or so on the scope, but the machine appeared to move
smoothly.Â* I guess the Y-axis thrust bearings were so wore out that it
allowed it to move smoother.Â* With new fresh bearings it pulses badly.
And no its not a matter of tuning.Â* As near as I can tell the ballscrew
is bent and its binding as it turns.Â* That would sure explain the
chatter I saw before.Â* Now its unusable.

The bad part is I don't know how to remove the new bearings and save
them.Â* The obvious way to pull the bearings pulls the rear bearing apart
when you take the housing and bearings off the shaft.Â* So... even if I
find a good replacement ballscrew I'll wind up having to chase down
another set of bearings too.

Of course I have one piece to make to finish a job that is just a little
too big for the little mills.

DANG-IT!




I've got some much smaller cheap Chinese double nut ball screws on the
shelf. I'm right at that point where I am tempted to make an adapter
plate to mount the ball nut for one of those, and make my own bearing
and motor mounting plate for the front of the machine. It probably
wouldn't last long, but it should be reversible. I'd have to direct
drive the screw which would leave the motor sticking out in the way in
the front of the machine. Its not a pleasant solution. Atleast I could
make all the parts on the little high speed machines, and then I might
be able to finish my current job.