PM25MV DRO resolution questions

I apologize for tacking on to an older thread, but...

My DRO is from PM and came mounted on my PM-727M and I, too, am confused about the resolution setting. This thread has provided some good clues. I recognized that the DRO may not be the same unit, but it has given me a similar problem to the OP's.

I set my resolution to 0.1um and found that the display would read half of the actual distance traveled but would increment the readout in 0.0001" steps. Setting the resolution to 0.2um corrected the display (it reads the actual distance traveled) but now it increments in 0.0002" steps! I'll try the suggested 5um and see what I get.

Or is there something else I'm missing?
 
The only scale I have that reads .0001 steps is the cross slide on my lathe, and it's a different scale (resolution) than that on the carriage. The DROs I have (and have had before) on my mills read .0002" steps and they are all the same resolution. These are DroPros DROs.

I was told (by someone here) that mill scales step in two tenths increments because a mill is not as accurate as a lathe and doesn't need the finer resolutions scales.

Don't know if it's right or not, but I'm lucky to get within a half-thou on a mill for really tight stuff and normally consider +/- a thou to be good enough in most cases. But that's just me. :)

Edit: The suggestion to call PM was a good one as they can tell you what scales were shipped with the mill.
 
I recently bought a PM-25MV and a PM-1030V, both with factory installed DROs. The only configuration change that I made was to change from metric to imperial.

Both of my DROs read out to .00001”, but the smallest adjustment that I can make is just about .00020“, which goes along with what somebody posted earlier in this thread. Put another way, the smallest adjustment that I can dial in is 2 tenths.

I left the DROs as they were when they came (i.e. showing the hundred thousandths), but I ignore the last digit, of course.

So, for example, when I dial in a 4 tenths depth of cut, the DRO shows .00039”. Similarly when I dial in a 2 tenths DOC, the display shows .00020”. I consider .00078” to be 8 tenths, and so on.

Ignoring the last digit and rounding to the nearest tenth was an easy adjustment.

I am often dialing in just a few tenths so I actually appreciate being able to see such a small level of resolution.

Compare the table DRO (with its ability to dial in 2 tenths) to the DRO for the quill which shows to the nearest 5 tenths.

In my experience, locking an axis or quill will often change the value on the display by a few tenths. If this is a problem for me, I don’t lock the axis or quill and watch the display to see if it moves during the cut. So far, the position of the axis or quill has never moved on these very light cuts, even while not locked!
 
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I too have a PM727V and a PM1030V, both came with the DRO installed. The DRO sensors are metric instuments with a granularity of 0.005mm. That is just less than 0.0002 (actually 0.00019685039 inches) . The DRO computer converts it, but I don't know what algorithm they are using for the conversion and rounding. I love the the DROs, not having to worry about backlash too much and counting handwheel revolutions. My skills and needs are in the +/- 0.001 range. All good here.
 
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