RE: [CAD_CAM_EDM_DRO] Which to trust, home-built DROs or hash marks?

Don't trust the leadscrews in the mill/drill. When I first gotmoni I
took it apart because there was a bind in one spot on the X axis. After
I reassembled it I started checking it with my dro and was coming up
with a difference but I was using usdigital linear encoders. So after
messing with both of them for a while I went back and got out my long
drift dial indicator with a 2" travel. I removed the backlash and then
was shocked to see that the dial indicator matched the dro so that
verified that the acme leadscrew pitch was off. It was a consistent .001
per inch. Using various methods I verified that in 10" it was .010 off.
So I quit fooling around with it and retrofitted it to ballscrews and
cnc and am glad that I did.
Dan