# Dro Advise



## jbolt (Apr 28, 2016)

Hi All,

I had originally ordered the PM-1440GT with a DRO from PM that I will install myself. It is the glass scale version he sells. My only experience with DRO glass scales is the SINO DRO/scales PM put on the PM1127 we got for the high school. Both scales failed within the first two years of limited use so I'm a bit gun shy of them. It could just be the SINO brand or a bad batch since there are so many out there. 

My old lathe had a Shooting Star CBX DRO that used a rack and pinion scale. Good for 0.0005" and worked really well for a long time but the scale read heads are large and the rack gear covers are crude at best. I usually do my high precision work with indicators so the standard resolution did not matter.

I'm now re-thinking the glass scales and going to the newer magnetic scales with higher resolution. 

I use my lathe a lot and the scales will be subject to cutting oil, coolant, solvent etc. I would love to hear some thoughts on either. I won't be able to order until the new lathe arrives but I will need to make a decision before it is shipped (hoping next month).

Jay


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## wrmiller (Apr 28, 2016)

Hey Jay,

Well, you're asking for opinions (read highly subjective and emotional), but here goes. 

On my 1340GT I broke with my previous usage of DroPros glass scales (on three different mills) and went with the DroPros EL400 and magnetic scales for a couple of reasons: One, I can cut them to length, and two, they are more resistant to contamination from coolant and flying debris than glass scales. Note that I said 'resistant' as opposed to 'impervious' as I am not sure such a scale exists. But, they have performed well so far. Truth be told, I have not had a single scale fail on any of my DroPros DROs (I have used the Easson GS30 scales exclusively), but I only use a FogBuster, not flood coolant. And I am very picky about getting my scales properly aligned to reduce the chance of failure or errors.

Interestingly, I too used a Shooting Star on my very first mini-mill many years ago. But back then if I could repeat to a thou or two I considered that good enough and the Star was plenty good enough for that.


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## sanddan (Apr 28, 2016)

I have glass scales on my mill and lathe. The mill came with a 3 axis DRO installed, Meister brand, that is old enough that the connectors are the old round style that's not used anymore. Still functions great. I also installed a 3 axis DRO I purchased from ebay on my first rf45 clone mill that I used for 3 years without issue. That unit had the best display of the three that I've used so far. I got an Eassson 2 axis from PM for my PM1340 lathe that also works fine. I don't like the display as much as the other systems I've used but it's more of a personal preference than any serious defect or problem. I wish I'd went with a better display, the glass scales are ok for me. If price is no object go with the EL400, it's also a dedicated lathe display which is a plus in my mind. I would also install the DRO myself and buy the kit from DRO pros as they have better brackets supplied with the kits. I ended up making all new brackets when I did my install as the supplied brackets were pitiful. If it had been preinstalled and worked ok, the quality of the brackets would not have mattered but I could not use them when doing the install myself. I guess I have my own minimum standards that I have to meet. 

I think the display is more important to be happy with than the scales as that is the part of the DRO that you interact with every time you use the lathe. The most important decision is to just GET THE DRO. You won't regret it, wish I'd got one sooner.


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## jbolt (Apr 28, 2016)

I would not use a lathe or mill today without a DRO. I learned to machine before DRO's were common. I have no intention of going back to counting turns and using grease pencils to mark the dials. 

I will probably never get away from using indicators for certain work. Indicators allow you to see what is going on near the cutting edge vs. some fixed point on the saddle or cross slide several inches away. 

I'll differ on I think the quality/accuracy of the scale/reader is more important that the display configuration. 

I will do the install myself. I'm a little picky about that kind of thing. I have read the glass scales a more prone to contamination issues. That is one of my concerns with using coolant. From using coolant on my mill I know how tenacious can be about getting into places you would not think possible.

Bill- I used the CBX for 14 years. It would repeat to 0.005" with the machine properly adjusted. A few years ago I pulled them off to inspect and clean. Despite the crude split loom covers the racks were clean and the pinions and encoders had no sign of contamination. I was surprised since I never had a shield over the Z-axis.

Have you had any issues with ferrous metal chips causing problems with the magnetic scales/heads? I looked at the DRO Pros install videos and I was surprised the scale covers did not have closed ends?


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## mksj (Apr 28, 2016)

I use the Easson ES-12 display with their glass scales on the PM1340GT which was installed by QMT, I just prefer the graphical displays to the straight numeric types. The ES-12 is color and you can change the display colors, etc. Never have had an issue with the glass scales, both are well covered, they offer the same resolution as magnetic, usually 5 micron and 1 micron. My mill has an Acu-Rite VUE DRO with their glass scales which I installed, very similar to the ES-12, but about 25% more. It does have a USB, so you can update the software.  Top of the line would probably be what Bill has on his mill, EL-700 is very nice, has some neat features like if you put a scale on both the cross slide and tool post slide, it gives combined directional movements at any tool post slide angle. But you are looking at twice the price of a standard 2 axis DRO system.

On the coolant issue, glass scales have been around for a long time, the better ones with proper covers rarely have an issue with contamination. The magnetic ones also need to be covered and setting the gap is very important to prevent errors. I have heard of a problem with ferrous chips interfering with the magnetic reader, old post in this forum. Properly installing them and a shield are important factors to keeping them happy.


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## wrmiller (Apr 28, 2016)

jbolt said:


> Have you had any issues with ferrous metal chips causing problems with the magnetic scales/heads? I looked at the DRO Pros install videos and I was surprised the scale covers did not have closed ends?



None to date. The reader head on the mag scales has these little plastic 'wipers' on each end that will prevent anything other than powder from getting under the head, and if the height is set correctly there is no gap on the sides either (I actually set mine so the plastic gauge is a bit snug). I don't have a scale cover over the long scale. All I have is a small 6'-8"? piece of flat aluminum strip over the reader head on scale on the back of the lathe bed (I keep forgetting what axis that is... Z?) and it has performed flawlessly since the install. And it's down there behind the bed where all the chip coils gather.


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## mksj (Apr 28, 2016)

The magnetic scales work very well, but a few people have had some issues. I still think it is reasonable to put a simple cover over them to just minimize the risk over time that something is going to get between the scale and the reader. If I recall, I think it was Jim Dawson who previous had one start to give errors, and it was a filing between the head and the scale. Mounting is also important, I use small jack screws in the corners to align the scales, usually mounted them to a solid back plate. Do not get me wrong, if the magnetic scales weren't twice the price, I would have gone that route, but no regrets with the glass scales either.
http://www.hobby-machinist.com/threads/magnetic-dro-problems.30201/#post-260444
Nice install of magnetic scales by Coolidge.
http://www.hobby-machinist.com/thre...-dro-magnetic-scale-kit-install-1-of-2.21226/
http://www.hobby-machinist.com/thre...dro-magnetic-scale-install.21299/#post-185831


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## jbolt (Jun 23, 2016)

wrmiller said:


> None to date. The reader head on the mag scales has these little plastic 'wipers' on each end that will prevent anything other than powder from getting under the head, and if the height is set correctly there is no gap on the sides either (I actually set mine so the plastic gauge is a bit snug). I don't have a scale cover over the long scale. All I have is a small 6'-8"? piece of flat aluminum strip over the reader head on scale on the back of the lathe bed (I keep forgetting what axis that is... Z?) and it has performed flawlessly since the install. And it's down there behind the bed where all the chip coils gather.


What kit did you use, 8x40, 10x40 or? I'm curious what the actual cross feed travel of the 1340 is vs. the published spec.

Sent from my SAMSUNG-SM-G900A using Tapatalk


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## wrmiller (Jun 24, 2016)

I don't remember. I. Did have to trim the cross-slide scale, so I probably bought the 10". I didn't have to trim the long scale.


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