David,
Digital calipers costing less than a tenner can easily be modified to fit for uses such as yours, my old mill used to have the digital type scales on all three axis and they worked just fine, as long as you can keep swarf and moisture out of them.
A quick strip down, clean and dry out got them up and running again. Oh, and a dozen batteries in stock, once they get wet, the scales tend to eat them like they are going out of fashion.
I still use one on my new mill, for the quill feed, and it works perfectly. But I have fitted a remote readout, and a mains transformer kindly supplied by another member on here. Only because of me, making life easier for myself.
They are usually accurate to 0.0005" (0.001mm)

I have gone over the top with my machines, but you would find, even cheapo scales can allow more accurate and easier use of your machinery, and can transform difficult jobs using handwheels, into run of the mill machining exercises.
John