Re: MaxNC Gib Adjustment

At 08:27 01/11/00 +0000, you wrote:

>Now that I know how to "lock" them, I'm still left wondering if there's any
>specific (proper) way to adjust the four screws on axis? Why are there
>four and not just two set screws (the gibs seem fairly rigid)? I assume
>you want the gib parallel to the opposite side? But how does one know when
>it is? Should it be adjusted to leave a tiny bit of play?

The gib may appear rigid, but it will inevitably flex under load. Four
screws gives a better chance of keeping it from flexing, and keeping it in
contact with the ways over its full length.

What you're looking for in adjusting the gib is to remove all play, and yet
not tighten the gib to the point where the the slide binds. Obviously,
there is no point in having the gib so tight that the stepper motor will no
longer drive the axis. On my Taig mill, I find the easiest way to get the
feel for this adjustment is to unbolt the stepper motor mount and remove
the leadscrew for the axis concerned, so that you can move the slide by
hand. For the Z axis, I also remove the spindle motor, to make sure that
the weight of the motor is not taking up any play that there may be in the
Z ways.

If you leave any play in the slides, this will translate into inaccurate
positioning of the work/spindle & increased vibration/tool chatter.

Over time, uneven wear in the ways will make it harder to remove all of the
play while still allowing travel over the full range of the axis without
binding, so this adjustment becomes more of a compromise as time goes on -
especially with small machines like these that have relatively little power
to drive the axes.

Regards,
Tony