Which would be more accurate for a servo based setup using a step
compatible drive;

1. Use screw TPI, gear ratio data, encoder CPR etc. to arrive at step
resolution for X, Y and Z axes

or

2. Use 1 above then fine tune using el cheapo HF dial indicator on each
axis under software control

Using dial indicator seems standard for backlash measurement.

wrote:

Which would be more accurate for a servo based setup using a step
compatible drive;

1. Use screw TPI, gear ratio data, encoder CPR etc. to arrive at step
resolution for X, Y and Z axes

or

2. Use 1 above then fine tune using el cheapo HF dial indicator on each
axis under software control

Using dial indicator seems standard for backlash measurement.

You have to use #1 to determine your steps per unit setting.

The dial indicator can give you the backlash amount if your controller
software supports backlash compensation. Backlash compensation doesn't
work particularly well, so it's best to adjust things mechanically to
get the least possible backlash.

If your controller software supports a pitch error mapping table, you
can tediously use the dial indicator to map the pitch errors of the
screw along the entire axis travel.

Pete C.