um, is the dro acting wierd?

i just noticed this the other day when drilling a series of holes in a
plate.

all measurements were spec'd, i just had to read off the dro to get my
locations.

after the second hole going onto the third, i noticed that what i was
about to drill did NOT match up with the dro reading. it was off. so i
stop and check my math, etc.. this happened all throughout the operation.

same operation yesterday and noticed it again after zeroing x and y.
knowing that something was wierd, i ran the axes to random points to check
before i started drilling.

and then the strangest thing. i saw the dro literally jump by .200" by
itself. WTF? it happened all over the place and ONLY in the y axis. from
1.000 to 0.800., etc..

so, is this my scale? dro? cable?

you can see the setup at my site. it's the chinese scales and dro like you
see at lathemaster.com.

thanks!

--

here's the hf mini mill dro/cnc mod!
<http://www.fignoggle.com/~fignoggle/hFCn66Ghejx8Jwia3Kl32ReQ/themachine/>