On 3/17/2012 5:26 AM, Dennis wrote:
I've just test run a little CNC router / mill I've put together.

At the moment I'm using M10 x 1.5mm pitch allthread for the lead screws and
PVC blocks for the nuts.


I've calibrated the axes (Mach3) using the 1.5mm leadscrew pitch and the
known motor steps/rev.


With a dial gauge on an axis, when I do a 1mm move sometimes I see 0.90mm or
0.95, sometimes 1.0. It seems repeatable, ie if I reverse the steps I see
the same values.

What do people think? I guess this is typical for cheap bit of allthread
from the local hardware store?


ACME leadscrews are on the drawing board when finances are willing....


How much does the leadscrew, itself, move when torque is applied? Some
movement must be caused by the thrust bearings at the ends of the leadscrew.

Paul