# 20" Linear Digital Scale Dro



## Pat of TN (Apr 20, 2015)

Hello gentlemen, I've a question relative to a cheap DRO.

I found this item on Little Machine Shop's website:

http://littlemachineshop.com/products/product_view.php?ProductID=5012&category=-1536942993

I really like it! Seems like a neat little item. Easy-to-install DRO with a remote display, a lot less cash than similar-price full DROs. No fancy features like bolt circles and etc., but that's what CAD programs are for.

What is not quite apparent is how to mount the moving slide to a stationary part of the machine. I will probably shoot Chris at LMS an email about this.

Anyway. I will be having a brand-new PM25MV within the next few weeks, probably like several else here on this board. I would like to have some type of DRO-type capability on it, but I'm not keen on paying $700 or more. Not at the moment.

In milling a pocket, backlash is a killer. DROs save us from the evils of backlash. A PM25 has 19" of travel, according to Precision Matthew's website. Does anyone know of an item similar to that above, with enough travel to nearly cover or more than cover 19" of travel? I've hit up Google, with few results other than Mitutoyo, which are equal in price to a full DRO...

I have found this item on eBay, but I feel a little dubious about an unknown item from eBay: http://www.ebay.com/itm/like/360077691868?lpid=82&chn=ps

If anyone has happened to use that item or knows of an alternative, that would be wonderful. Thank you.


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## Franko (Apr 20, 2015)

The Little Machine Shop DRO is an IGaging Absolute DRO. They are pretty good. I have a set on my mill. A member of Hobby Machinist forum named David sells them for a pretty fair price and he is a very nice guy.

Usually the scale (long part) mounts on the side of the moving mill table. The sensor that slides on the scale has mounting holes on the back. You make a bracket and mount it to a stationary part of your mill that will reach. I put mine behind the table. If you want x-y axis, you can attach two of the Absolute DROs together. They each come with a mounting bracket and arm.

For your mill, you would probably need a 24" DRO for the x-axis. They come with just about all the mounting brackets you'll need, except for the sensor, which you have to make. The scales can be cut to perfect size. They are hardened so probably a composite cutting wheel will be required. The sensor in the scales is a black plastic strip. It should be protected from the heat of the cut. I used a couple bars of aluminum clamped on both sides for a heat sink.

Search DRO and there are several items where members have shown pictures of where and how they mounted them.


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## Franko (Apr 20, 2015)

Here is pic of how I mounted mine. I used a section of aluminum angle to shield the x-axis from chips and fluids. Since this pic, I made a thin flashing to cover the sensor on the y-axis. The y-axis scale is way longer than necessary, but I didn't see any need to shorten it.


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## Pat of TN (Apr 20, 2015)

I like it, Franko! Neat. Basically you custom-rig a mount for the slide. Intriguing. One thing I have never done is drill & tap into a machine. As simple as punching your center point, drilling, and winging a tap in the hole?

How do you feel about the longevity of the device? My shop is unheated, uncooled, unhumidified, except by nature. I wonder how electronic displays last in that enivornment.

Any chance you could point me towards this David fellow? I'll look around too.

Thank you, sir!


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## Franko (Apr 20, 2015)

I do not know about the longevity of Absolute DROs. I've only had mine for a few weeks. Other members have recommended them. Maybe they'll know. I had another brand on my mill several summers and winters in my non-climate-controled shop in Texas, so I'm guessing they don't care much about the weather — especially hot weather.

David's username is DavidH. You should probably wait until your machine arrives so you can measure it to see what size you'll need. David just sells them and can't offer much technical support.

Drilling and tapping cast iron is about as easy as drilling and tapping wood. The swarf is very fine grained, about like firecracker gunpowder. It doesn't tend to tangle up in a tap. I used a smallish 12V cordless drill. I also use the 12V drill to hold and drive the tap. I just set the clutch about as low as it will go. You're only driving the tap in about a half inch. When I'm tapping cast iron like that, usually the tap runs in all the way in one go. When it bottoms out the clutch slips and you just reverse it out. Using the drill with a clutch, I've never broken even a very small tap. I feel I can hold a drill steadier than a T-handle tap holder.


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## RJSakowski (Apr 20, 2015)

Pat of TN said:


> I like it, Franko! Neat. Basically you custom-rig a mount for the slide. Intriguing. One thing I have never done is drill & tap into a machine. As simple as punching your center point, drilling, and winging a tap in the hole?
> 
> How do you feel about the longevity of the device? My shop is unheated, uncooled, unhumidified, except by nature. I wonder how electronic displays last in that enivornment.
> 
> ...


I have drilled and tapped a fair number of holes into the cast iron of machines.  Generally, they are fairly easy to drill and tap.  The chips are quite fine, no stringy things.  I have run into some hard spots in some castings.  You will know because all of a sudden, the driull comes to a stop and increased pressure is required to finish the hole. Be careful tapping those holes.  I broke a tap in my Grizzly frame on one of those.  fortunately, it was for a cover for the DRO so a non-critical hole and I was able to partially reclaim the hole although it took several hours of work.  Cast taps fairly well dry or you can use tapping fluid.  If you are tapping into an area where you don't want stray chips, using grease instead of tapping fluid and cleaning several times during the process will keep the chips contained.

The scales are capacitive sensors, the same as used on digital calipers.  The Absolute scales are on stainless backs while the liower cost ones are on aluminum.  Stainless will be better if in an uncontrolled temperature environment because it has better thermal expansion coefficients.  I put the aluminum backed scales on my lathe, mostly because of compatibility issues withe a third party readout (Google Yuriy for more info)  You should not have any temperature or humidity issues with the displays or electronics.

The fellow you are looking for is davidh.  He is up in Northern Wisconsin and I got my DRO's from him as well


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## Franko (Apr 21, 2015)

Thanks, RJ. I haven't run into any of those hard spots in cast iron. I'll keep my eye peeled for them in the future.

One thing that might be worth mentioning when installing DROs is to pay attention that you don't drill into the ways. That probably wouldn't be good.


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## Pat of TN (Apr 25, 2015)

Thank you gentlemen. I'll contact this David chap when I'm ready to get one, sounds like a good deal.


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## epj (Jun 4, 2015)

I have a similar device on a small milling table mounted on my drill press. Works pretty well, and I have been using it for more than a year without issues. They are not to be confused with a real DRO.


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## kingmt01 (Jun 5, 2015)

epj said:


> I have a similar device on a small milling table mounted on my drill press. Works pretty well, and I have been using it for more than a year without issues. They are not to be confused with a real DRO.


Really? DRO means digital read out. So your saying the read out isn't digital or what?

To the OP
I have these set up the same as RJ. I think we may even be in the same community for the bats testing of the app that uses these scales. I really don't have any issues with mine. But the ones you posted from LMS is way high on the price. I have a average of $40 a piece in mine and that is with scales that are up to 40" long. To get mine working on Android DRO I have about $200 a machine invested. That is each machine having all of its own parts. Everything you can move from one to another would save you money.


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## RJSakowski (Jun 5, 2015)

One point that should be made; the DRO systems using magnetic or glass scales have a sophisticated wiper system to prevent machining swarf and fluids contacting the scale surface while the iGaging type scales do not.  It would be wise to install protective covers like Franko has done above to shield the scale and pickup.


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## atunguyd (Jun 5, 2015)

Google for touch dro.  You can interface these igaging readers to an android tablet and get a full blown DRO with touch screen and all the features. Bottle patterns feed speeds tooth load etc.


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## brav65 (Jun 5, 2015)

atunguyd said:


> Google for touch dro.  You can interface these igaging readers to an android tablet and get a full blown DRO with touch screen and all the features. Bottle patterns feed speeds tooth load etc.



The DRO for Android is Yuri's Toys.  The software is a free download from the google store and his website has instructions on how to build the electronic interface for the scales to send the information to the android phone/tablet.  I have purchased all of the materials to build a DRO for my lathe, but not gotten around to building the whole system yet.  DavidH has the scales along with a number of other iGaging products for really good prices.


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## epj (Jun 5, 2015)

kingmt01 said:


> Really? DRO means digital read out. So your saying the read out isn't digital or what?
> 
> To the OP
> I have these set up the same as RJ. I think we may even be in the same community for the bats testing of the app that uses these scales. I really don't have any issues with mine. But the ones you posted from LMS is way high on the price. I have a average of $40 a piece in mine and that is with scales that are up to 40" long. To get mine working on Android DRO I have about $200 a machine invested. That is each machine having all of its own parts. Everything you can move from one to another would save you money.


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## epj (Jun 5, 2015)

What I'm saying is that the scales don't have the same degree of accuracy as a real DRO. They're close, and for many users may be close enough.


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## RJSakowski (Jun 5, 2015)

brav65 said:


> The DRO for Android is Yuri's Toys.  The software is a free download from the google store and his website has instructions on how to build the electronic interface for the scales to send the information to the android phone/tablet.  I have purchased all of the materials to build a DRO for my lathe, but not gotten around to building the whole system yet.  DavidH has the scales along with a number of other iGaging products for really good prices.


One should note that Yuriy's hardware and application do not work with the iGaging Absolute scales  (at least when I last contacted him last February).   See his website for more details and updates.


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## kingmt01 (Jun 5, 2015)

epj

The scales are rated +/- .0005 accuracy & +/-.001 repeatability. That is as good & better then most $500-$1000 DRO systems. With Yuriy's firmware & app I can read my scales to .0002 & they are within .0001 of that number out to 6" which is as far as I can measure to that degree. As far as repeatability I've never found them to be off. If I take a reading then run my table from one side to the other it is dead on. 

The biggest problem with them is they are known to be noisy which happened to me on my first setup but I had a problem with mine. When I first built it my voltage regulator wasn't dropping my voltage as low as it should do I added a diode to drop it more. Well after mine stopping to work I found the voltage to be to low by .5v the amount the diode was cutting it. I pulled the diode but broke my Bluetooth adaptor so it got changed out also. No noise at all in my unit now. I don't even use the filter that is built into the app. I also don't have the caps that the circuit calls for. I didn't have the caps his called for in the build & the ones I did have didn't make a difference when I tried them so I left them out.


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## epj (Jun 6, 2015)

Obviously this particular brand is more accurate than many. Most I've seen advertise accuracy and repeatability in the .002 range. I have one of those scales on my drill press. As I stated earlier, it works pretty well. I have observed the repeatability to be around .001, which is good enough for the drill press. The scales are a whole lot less aggravating to set up. If I had known I could get that sort of performance from scales, I could have saved a few hundred bucks. The only real function I've used the reader for is calculating 1/2, which I'm perfectly capable of  doing myself.


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## kingmt01 (Jun 6, 2015)

Actually mine are only advertised accuracy +/-.0005 "& repeatability of +/-.001" they just do much better then that. I can only read 10ths because of the android app. The head unit that came with them will only display to the nearest half thousandth.


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## epj (Jun 6, 2015)

Well, for many applications, maybe most, that's close enough.


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## kingmt01 (Jun 7, 2015)

That is probably better then my mill they are attached to can do. It see my table drift on my x axes often while doing operations. I'm sure my head is drifting up also so I always try to save .002" for a final cut.


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