I have a 2-axis DRO on my Grizzly G0709 (14" x 40") and a shop-made digital caliper for the tail stock; I love them both! Mine has 5 micron scales on both axis', resolution is ~0.0002" on the radius (Z) scale. Guys will recommend 1 micron scales for the Z-axis. In my experience (or lack thereof. . .), I've found the 0.0002" resolution to be "good enough". I don't trust the DRO if it's ultra-critical; measure with a micrometer and adjust accordingly.
The X/Y-axis is really nice for shoulders and hitting features down the length of work. All of my grooving and parting tools have their width written on the tool holder. Need to cut off a 1.00" length from a rod? I butt the tool bit up to the end of the stock, hit "X/Y", enter the tool bit's width, hit ENTER. Then move the carriage down to my mark and part/groove, or whatever. I do the same operation on my Clausing lathe without a DRO using a dial indicator magneted to the bed. DRO is much more convenient.
Regarding the tailstock caliper, it's really not necessary, but it's nice! Want to drill a hole 3/4" deep into stock? Center drill, drill in until I eyeball depth while advancing the drill bit until I hit the full diameter. Zero the caliper and plunge away.
Bruce
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