# DRO for PM-25MV



## Steven57 (Dec 19, 2014)

Have been researching and consensus seems to be that digital scales stainless are accurate enough for the mill. Anyone think otherwise as in glass/magnetic?

And while we are st it, what about PM-1030V? Stainless scales or full DRO glass/magnetic?


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## wrmiller (Dec 19, 2014)

If you believe those are what you want, go for it. Who cares what everyone else thinks? 

Just for the record, I use 3-axis glass. But that doesn't mean you should.


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## Steven57 (Dec 20, 2014)

Actually, I was wonder who was using what and their real life experience. Statements like "I have the stainless and wished I had glass/magnetic" or "Stainless works great for me on this mill".


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## wrmiller (Dec 20, 2014)

Ah, got it.  

The glass 'might' be over kill, but who's to say? I really like mine and the accuracy I get from them. You also have to remember that different folks have different situations and will make do with what they can get/afford. For me, I would have loved to get the magnetic scales but just couldn't afford it (justify it?) at that time. Would the magnetic have been better? Don't know.

Another example: When I bought my first mini-mill 12 years ago I bought a small 3-axis DRO from a Canadian company that used toothed rods and gears for scales (sorry, can't remember the name off-hand but they still exist) and while I thought it was kinda funky from a design perspective the little stinkers actually worked quite well!  

Point is, most of this stuff will work fine but it won't necessarily prevent people from wishing for something different. What are the goals you are trying to achieve with your machine/DRO setup? What kind of projects are you thinking of doing and what kind of accuracy are you trying to achieve?


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## brav65 (Dec 20, 2014)

Steven57 said:


> Have been researching and consensus seems to be that digital scales stainless are accurate enough for the mill. Anyone think otherwise as in glass/magnetic?
> 
> And while we are st it, what about PM-1030V? Stainless scales or full DRO glass/magnetic?




I chose to install DRO Pros 3 axis with glass scales.  The model is the 3M, and and came with great support literature and appears to be good quality.  I have not used it for very long, so cannot comment on service life.  The readout has a number of useful features that I am still learning to use.  It is a very intuitive system that does not require you to have the manual at hand every time you want to try out a feature.


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## Steven57 (Dec 21, 2014)

Ideally I'd like accuracy to .001 and it seems that is doable even with the stainless digitals. Everything I intend to do would be just for me or friends and would generally be replacement parts, jigs, and a couple precision pieces I have in my head. As long as the screw/bolt holes line up I'm good with that. I understand the standalone 2-3 axis glass/magnetic systems have features/functions that the digitals don't. But, if I have my math down the digitals can get the job done. 

So, after all of that I guess I'm asking are the stainless digitals accurate enough or not for the PM-25MV? Or, is the mill capable or not of reaching the accuracy of the glass/magnetic systems?


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## wrmiller (Dec 21, 2014)

I have done half thou and less work on my PM25, which is more than I typically need as a hobbyist. 

The trick with the PM25 or any of the smaller bench mills is to remember that these things are not very rigid and WILL flex as a function of how much load/cutting forces are placed upon them. When roughing in, you don't pay that much attention to part/machine flex other than to note how much in preparation for dialing in the next cut.

When you start getting close to your final dimensions, taking smaller cuts will reduce the machine/tool deflection (cutters flex too) and permit you to achieve your final dimensions without too much drama. To hold to a thou dimensional variance seems to be everyone's goal, but remember that even on a Bridgeport an experienced machinist doesn't try to hold any better than that (so I'm told). That's what surface grinders are for.  

In my personal experience, I DO like to see those tenths on the readout (.0002) as that helps me 'fudge factor' for part/tool deflection as I'm sneaking up on final dimensions.


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## JimDawson (Dec 21, 2014)

Can somebody provide a link to ''stainless digitals'', this is a term I've not heard before.


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## Steven57 (Dec 21, 2014)

Here's a link to one.

http://www.amazon.com/AccuRemote-AC...9183668&sr=8-2&keywords=stainless+digital+dro


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## chuckorlando (Dec 21, 2014)

Stainless are more or less just a digital caliper with a remote read out. I have 3 axis igaging and they work awesome. I mean if it needs to be nuts on, you should not rely on a read out IMO no matter how much it cost. You can bout hit a .0001 on the stainless but it would be hit or miss I assume. It flash a half mark or something to that effect. But to stay in side a .001 or so, they work great.

But the functions in the real dros is where the money is at. That and the oil/coolant proof. As well as the .0001 reading as I I watch them when I get a thousandth  over


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## GA Gyro (Dec 21, 2014)

With my new PM935TS mill  (BP clone), I ordered an Easson '12' DRO... pricy.
This DRO came with glass scales mounted, Matt and his crew did a good job of mounting the DRO.  

The mill is set up and running, and the DRO reads in 'tenths'... however getting the mill at a specific 'tenth' location with the table and knee cranks would be an exercise in minute movement... doable... yet something one would have to 'creep up on'... CAREFULLY... :shush:  

What WRMiller mentioned in a post earlier... about robust roughing cuts and then fine finishing cuts... remembering machine, tool, tool holder, spindle, and even work will flex under the load of the cut... is reality.  
Knowing how to 'creep up to' what you intend to end with... is different than just setting the dials and let it cut.  This takes practice... and experience... 

If it were me... I would get something a bit better than what you can envision today... as IMO when one learns more (and gets more practice and experience)... their expectations of what they want to do (and can do) will expand.  Getting something 'economical' (read that cheap) now... then having to replace it later... well how much $$$ has one spent cumulatively?


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## jimcisme (Apr 4, 2016)

wrmiller said:


> I have done half thou and less work on my PM25, which is more than I typically need as a hobbyist.
> 
> The trick with the PM25 or any of the smaller bench mills is to remember that these things are not very rigid and WILL flex as a function of how much load/cutting forces are placed upon them. When roughing in, you don't pay that much attention to part/machine flex other than to note how much in preparation for dialing in the next cut.
> 
> ...


I totaly agree. Very well put.


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## jbolt (Apr 4, 2016)

wrmiller said:


> Another example: When I bought my first mini-mill 12 years ago I bought a small 3-axis DRO from a Canadian company that used toothed rods and gears for scales (sorry, can't remember the name off-hand but they still exist) and while I thought it was kinda funky from a design perspective the little stinkers actually worked quite well!



That would be the Shooting Star CBX DRO. I had one on my Smithy Granite 1324. That was the affordable system at the time in 2001. 

The rack and pinion system works very well. The read head is an optical encoder driven by precision gears. The split wire loom covers for the rack gear work fine for general use but would not work with heavy coolant use. Mine was powered on 24/7 for 14 years and the only issue was a failed wall wart transformer at 11 years. The owner helped me troubleshoot the problem on a weekend and helped me find a suitable local replacement. Excellent customer service. At their price point there are better offerings now.

We have had two SINO glass scales fail on our PM-1127 in less than two years. Fortunately they were replaced under warranty but it makes me wonder about the longevity of the low cost import glass scales.


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