Hi Charley
I have been down the road with eye sight problems, and at first tried to re-do the grads on the dials. Then thought ok, I will just make new dials with deeper grads thinking that would help. It did, but was marginal at best. The mill got a DRO years ago. The lathe has had one now for a few yrs.
The milling machine has the Newall C-80 3-axis. The scales are those stainless steel tubes with balls inside them. They are the ones they claimed could be submerged in coolant, and not bothered by chips and such. I was a very pricey DRO and have not had any troubles with it. The price of that DRO made me re think about the purchase of the next one for the lathe.
The lathe has a SINO 2-axis DRO, with glass scales. The Sino has all the features of the hi-buck unit, but at a much lower cost. The glass scales did come with much better shielding than the Newall did. Im assuming they needed it. I was a bit paranoid with the sino,s glass scales at first, thinking that might be the first thing to fail, but they havnt so far, touch wood, haha. I do clean my machines after each days use with the shop vac. The may help the DRO live a little longer, don,t know.
The Newall was installed far enough back when the eyes were fine. I just hated dealing with back lash. The Sino was installed because of eye sight problems. I had looked at the lower cost setups like Igaging, but the reader heads remind me of what I see on a digital caliper, and find they are not lit up, and hard for me to see. Atleast they were back then, maybe they have changed now, dunno.
Eye sight good, or bad. The DRO will make your life so much easyer. I think I would choose your DRO according to how bad the envirment is. I would think a surface grinder would need something really well shielded.