Fitting a 5 micron DRO to Myford ML7

If the OP is worried about that last umpteenth signicant figure, I suggest he uses a suitable micrometer to make his final measurements.

DROs are good enough for most things, but clearly the OP is not wanting to make confirmation measurements with a standard measuring device which can be checked against sufficiently accurate standards - like a set of gauge blocks.

My cheap DRO set indicates to 0.01mm and obviously has tolerances on accuracy and precision, but is good enough for most machining operations. For most modellers, I reckon the ‘fit’ is more important than the absolute accuracy. They are not making serial machines or parts for production items. How many drawings even require dimensions to those tolerances? That is outside of science/NASA/etc requirements.

The 0.001mm set is clearly better than the cheaper set - but would I always actually trust that last digit to be absolutely accurate? No, because there are always errors involved in making any readings.

A spec of sawdust and a plank comes to mind…

Could be, except they aren't!

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Then, evidently, I chose my word, and its underlining appropriately.

MichaelG.

Im with NDIY its not the size its the fit!

No

The DRO on a lathe does not tell you the size of the work piece, only the travel of the carriage or cross slide assuming a read head runs exactly parallel to the scale and the mountings are not flexing.

That then leaves tool deflection, tool height, head bearing wear, blah blah.

What they are good at is telling you when backlash has moved a supposedly clamped cutting depth and save having to count the number of turns on the carriage/leadscrew handwheel especially on lathes like mine that does not have either graduated. They also confirm that a spring cut is just that though only a mic can tell you if you should be taking one in the first place.