"Ecnerwal" wrote in message
...
In article ,
"Bob La Londe" wrote:

When I mounted the chuck on the table it was my intention to convert it
to
CNC eventually. Both of my little machine controllers have an unused 4th
port. Its would just be a matter of making a mount and adding a motor.
The
problem I see is that the drive screw for this rotary table has too much
back lash in it. I have not looked yet to see if there is anything I can
do
about it, but I was thinking it might be easier to just make a spindle
for a
4th axis. I was thinking I would like something with a much bigger bore
than the average lathe spindle or rotary table. If I keep it under 3000
RPM
there are some pretty big bore bearings out there.

With good programming, lash (at least consistent lash - and with fancy
enough programming, I suppose arbitrary lash) is as little an issue as
your ability to measure it - just tell the drive to compensate, and have
some sort of homing routine so it has a known point to start
compensating from.

There's also the simple approach, which is to always rotate the same
direction - just as you were planning to do by hand. If you need to be
CCW 1 degree, go CW 359 degrees (or vice versa)

Yeah, I thought of that too. I still want a large bore 4th axis. There was
an awesome huge chuck that sold on Ebay recently, but I decided I needed
servo drivers for my big mill more than I needed a chuck right now.