# PM25MV DRO resolution questions



## javaduke (Mar 2, 2019)

OK, so there's something I'm clearly missing but I couldn't find any answer in the manual. I expect the reading on the DRO to be the actual travel distance on the respective axis - i.e. 1 inch of X axis table travel should read as 1.000 on the DRO. So I set the resolution to the 1.0uom. What I see is that 1 inch of travel results in the 2.000 on the DRO. So In order to get the actual distance displayed I had to set the resolution to 0.5uom. Doesn't  really make a lot of sense to me. Am I missing something or is it how it is supposed to be? 

Another question is, how can I reduce the number of positions after the decimal point? My DRO currently displays 6 digits after the decimal point, and I really don't need that kind of precision, a 1/10000 of an inch would be enough.  Is there any setting for that? I studied the manual but couldn't find any answer.


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## mmcmdl (Mar 2, 2019)

javaduke said:


> What I see is that 1 inch of travel results in the 2.000 on the DRO



It makes sense for x axis on a lathe . I'm sure somewhere in your manual will tell you how to change settings including your trailing 0s . Most are set for .0005 in shops , anything closer is utter nonsense . It isn't a jigbore .


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## darkzero (Mar 2, 2019)

If you are seeing 6 digits after the decimal you have the micron setting wrong. If you have 1um scales, set to 1um, if 5um scales then set to 5um. This should give you 4 digits after the decimal.

To get the X axis to read actual travel set the radius/diameter mode in settings to radius. Some DROs also have a R/D button which will allow you to switch back & forth quickly without having to make the change in the settings.

Edit: Oops, just realized this is a mill, no matter, the settings are the same. Just make sure you have the DRO set for Mill in the settings.


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## javaduke (Mar 3, 2019)

Hmmm, interesting, I just checked my settings, mine reads MILL 3 - which is what I expected, but I still can only get actual readings when I set resolution to 0.5um.
Don't think it has any radius/diameter setting - at least I couldn't find any mention of it in the manual.


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## darkzero (Mar 3, 2019)

It should. All 3 DROs that I've had (different brands) all had it. Which DRO display do you have?


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## javaduke (Mar 3, 2019)

I have the one that came with the machine. Here's the manual for it: http://www.precisionmatthews.com/wp-content/uploads/2017/01/PM-DRO-Manual-1-15-2018-Web.pdf


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## Landmark (Mar 3, 2019)

Most inexpensive Chinese glass scales have a resolution of 0.0002 ( 2 tenths) which is 5um. To simplify a DRO counts ticks from the scale reader. Each tick is 0.0002" so setting the resolution to 5um lets the DRO know how far the axis moved for each tick.


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## darkzero (Mar 4, 2019)

javaduke said:


> I have the one that came with the machine. Here's the manual for it: http://www.precisionmatthews.com/wp-content/uploads/2017/01/PM-DRO-Manual-1-15-2018-Web.pdf



Yeah I don't see the setting either. My guess is with your DRO, when set to mill mode it automatically sets it. You mentioned that you set resolution to 0.5um. did you actually set to 0.5um or 5um? 5um & 1um is most common. Assuming you have 5um scales, try setting to 5um instead of .5um.


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## MSD0 (Mar 4, 2019)

I would ask Matt. I’m surprised it wasn’t already set up (or included a quick setup guide at least).


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## dcsleep (Mar 4, 2019)

I have a PM-25MV with the PM-installed DRO which was purchased last June. My DRO resolution is set to 5um and there's a separate setting ("INCH DOT") which can be set to either 4 or 5 significant digits.


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## BobRock (Jan 13, 2020)

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?


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## wrmiller (Jan 13, 2020)

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.


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## erikmannie (Jan 15, 2020)

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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## starr256 (Jan 17, 2020)

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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