Lathe DRO from Digital Caliper .. 10 Bucks .. 6" caliper has range of entire 16" bed

[mklotz]

One point I think worth mentioning here for anyone doing this is the caliper choice. The calipers from Harbor Freight have an auto off function that on the decimal/mm caliper turns back on at 0.000" whereas the decimal/fraction/mm model turns back on at its last known setting, this can be a real problem if you stop to look at plans / think about your next step etc. and the caliper auto-offs requiring you to re-start your settings from a known point! I highly recommend using the unit that starts from its last known position.

Many of the cheap import calipers, such as those sold by HF, memory or not, have their measurement electronics on all the time; turning them off merely turns the display off. This constant drain on the battery means they eat batteries rather quickly.

In a fixed application like this, an external power supply would be a very good idea. Make an SR44-sized button of non-conductive material, glue on some thin electrodes to which are attached some fine wires and stick it in the battery compartment. Attach a 1.5 volt D-cell to the wires and you won't need to worry about mid-job battery failure.

This high rate of battery consumption seems to be a feature of the cheap calipers coming from China. I have two Mitutoyo calipers (Japanese), one with no memory and the other with memory, and they both go years before needing a new battery.