Info about DROs

Hi all,

This is a very interesting thread for me. I have a Chinese made X5015 milling machine which would really benefit from having a DRO fitted. I'd like to know if anyone has had the experience of fitting a DRO to a small mill and whether there are any Gotchas to be aware of. I'm thinking of taking the plunge for a 3 axis glass scale unit.

Thanks.

Moe
 
Hi all,
This is a very interesting thread for me. I have a Chinese made X5015 milling machine which would really benefit from having a DRO fitted. I'd like to know if anyone has had the experience of fitting a DRO to a small mill and whether there are any Gotchas to be aware of. I'm thinking of taking the plunge for a 3 axis glass scale unit.
Thanks.
Moe

I converted to 3 axis glass scale DRO last year and it was the best move that I have made in 30 years. The only gotcha is to insure that the glass scales are parallel and flat within .005" to the driven axis. A lot of shims and testing will pay off. My lathe uses cheaper magnetic Chinese DRO's which are a lot less critical in the mounting or alignment. Someday I will upgrade to Glass DRO's.
 
I have used a number of the igaging type inexpensive DROs (3 on the mill, 3 on the lathe, one on my drillpress). Here is why I think they are less expensive than the glass-slide type:

1) They don't have as much resolution capability. Many of the glass slide type DROs are capable of 0.0001" resolution while the igaging type are 0.0005" at best
2) They are much more susceptible to dirt and grit. See below.
3) The have a little backlash.
4) Better/faster electronics. Typically the more expensive units read very fast, while the igaging type read at a much slower rate, which sometimes slows one down in making a precise move.

Backlash: I have one of these digital scales on my 7x12 lathe cross-slide. I modified the cross slide to increase the travel, and I also changed the leadscrew nut to an anti-backlash design. In testing, I had the backlash down to about 0.001", but couldn't get it lower - it should have been almost zero. I was tearing my hair out until I put a dial test indicator on the slide and saw that the slide itself did in fact have immeasurably small backlash, and what I was seeing was the backlash in the digital scale. So users should be aware that there is a little, and if that's important to always approach a critical measurement from the same direction that the scale was zeroed. I don't know, but I suspect the more expensive readouts don't suffer from this.

Dirt: I can say from personal experience that fluids and grit will screw up these inexpensive units fairly quickly. When they get dirty, their behavior is very erratic to the point of being useless. I was able to restore two of them to proper operation by disassembling the sensor slide, cleaning with alcohol or electronic pcb flux remover, and them blowing them dry and blowing out any remaining debris with compressed air. Also the slide itself must be cleaned thoroughly. On my mill X scale and the lathe carriage position scale, I've now added covers over the scales, and that has helped a lot. The covers are basically the ones in the G0704 DRO mod shown at MadModder: http://madmodder.net/index.php?topic=6512.0 and they do a great job of keeping oil and grit and chips off of the scales.

Having said all that, the inexpensive units are a great value, and I can't imagine working without them.

bix
 
Guys! The cheap iGaging scales at 30% off at Grizzly right now! I'm not a paid advertiser, but am so excited I just ordered a bunch!

I used cheap scales I modified (***** to drill), and really liked it already.


Bernie
 
Ref the Grizzly dro's on sale:

Grizzly refers to them as suited for woodworking machinery vs the industrial quality, stainless steel (Grizzly's description) units immediately below on page 755 of the 2013 catalog.

While the sale items are not as accurate as the industrial quality (0.002/6 in vs 0.001/6 inches) what are the other differences? What relegates one (assuming the accuracy is adequate to your needs) to woodworking and the other to industrial (presumably metal machining)? Is there better sealing of the parts to moisture, lubricants, etc? Or... ?
 
Ref the Grizzly dro's on sale:

Grizzly refers to them as suited for woodworking machinery vs the industrial quality, stainless steel (Grizzly's description) units immediately below on page 755 of the 2013 catalog.

While the sale items are not as accurate as the industrial quality (0.002/6 in vs 0.001/6 inches) what are the other differences? What relegates one (assuming the accuracy is adequate to your needs) to woodworking and the other to industrial (presumably metal machining)? Is there better sealing of the parts to moisture, lubricants, etc? Or... ?

EDIT/ See post #13 , thanks bix. /EDIT

You have the correct idea. There have been numerous reports of problems related to jittery/jumpy/non-functional scales of this type. The issue appears to be the lack of sealing around the read head. Supporting this guess is the further reports of users restoring them by disassembling and cleaning the scales and reader heads.

That being said, the z-axis iGaging clone I installed on my Micro-Mark mill has been very reliable, and I intend to use the same type for the x- and y-axes too. But I will put a shield over them.

I can't see putting a $600+ DRO unit on my $700 mill, but these DROs are inexpensive enough, and accurate enough for my purposes to be useful. I have destroyed enough parts from loosing track of the position of the cutter on the work piece to justify the investment.

Walt
 
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Guys! The cheap iGaging scales at 30% off at Grizzly right now! I'm not a paid advertiser, but am so excited I just ordered a bunch!

I used cheap scales I modified (***** to drill), and really liked it already.


Bernie

What I'm seeing is the T23013 24" scale is marked down from $45 to $29.95.

http://www.grizzly.com/products/T23013

The claimed accuracy for this unit is +- 0.004" per 12", so it could be off by as much as 0.008". Certainly good enough for woodworking, and maybe some metalworking applications.

On the other hand, the T24362

http://www.grizzly.com/products/T24362

while not on sale, and costing $99.95, is claimed to have an accuracy of +-0.002" across the entire length. Note also that the shorter scales in this line are less expensive with equivalent or better claimed accuracy. The better ones are cheap enough for me to not find the sale item attractive, your needs may differ.

Walt
 
I have the stainless scales that you pointed out from Grizzly, and yes, they are indeed worth the extras cost as compared to the black ones. They're accurate, and they don't turn off on you until you're ready to.

Again though, if your work is not that fussy, then the black ones are fine.

Dave
 
While I am looking specifically at the stainless steel versions how does one size either version for a specific mill? From outside edge of the table to outside edge of the table (both X & Y dimensions)? My machine already has factory installed Z-axis readout. If the required dimension is between two offered sizes can the scale be cut? Dremel cut off wheel, fine-tooth hacksaw...?
 
I had one of the Grizzly I Gaging units on the Z axis of my 19" Jet drill press and it worked perfect. Was very accurate and repeatable. One of the nice things is about the I Gaging scales is they can be cut to size with no problem using a hack saw, dremel tool, ect. These scales must be magnetic which is what the high end DROs are using now. It is amazing to me how well that some of this cheap stuff is working these days.
 
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