source for glass scales.

[turbocad6]

I just got a touchDRO setup for my lathe and it is with Igauging absolute + scales which are fine for the little 7" lathe but now I am thinking about buying another for my big mill, always wanted a DRO on it but never got around to it. now since having the Igauging setup on the lathe I see what I have been missing with playing around with the dials all this time 

I have started looking at glass scales and I have come to realize that I can actually buy a complete 3 axis DRO with 3 glass scales for LESS than I can even buy just the 3 scales separately all by themselves... I'm just wondering if anyone else has noticed this or if anyone has any advice or maybe there is something that I m missing here? I mean to me it seems that it might just make the most sense to buy a complete DRO setup with scales and then just replace the actual DRO head eventually with a touchDRO setup, but that would mean of course that the actual whole DRO head itself would just be a waste. 

I don't get how it can actually be cheaper to buy a complete DRO and just throw the actual DRO head away, than it would be to just buy 3 glass scales, but this just seems to be the case here, I can get the whole DRO with 3 "5μm" scales that would be compatible with a touchDRO board for under or right around the $300 mark where I can't even buy the 3 scales alone for this much.... any thoughts?

[Yuriy]

I just got a touchDRO setup for my lathe and it is with Igauging absolute + scales which are fine for the little 7" lathe but now I am thinking about buying another for my big mill, always wanted a DRO on it but never got around to it. now since having the Igauging setup on the lathe I see what I have been missing with playing around with the dials all this time 

I have started looking at glass scales and I have come to realize that I can actually buy a complete 3 axis DRO with 3 glass scales for LESS than I can even buy just the 3 scales separately all by themselves... I'm just wondering if anyone else has noticed this or if anyone has any advice or maybe there is something that I m missing here? I mean to me it seems that it might just make the most sense to buy a complete DRO setup with scales and then just replace the actual DRO head eventually with a touchDRO setup, but that would mean of course that the actual whole DRO head itself would just be a waste. 

I don't get how it can actually be cheaper to buy a complete DRO and just throw the actual DRO head away, than it would be to just buy 3 glass scales, but this just seems to be the case here, I can get the whole DRO with 3 "5μm" scales that would be compatible with a touchDRO board for under or right around the $300 mark where I can't even buy the 3 scales alone for this much.... any thoughts?

A "fair" price for a Bridgeport-sized Chinese DRO (3 scales + console) is around $500-$700. At some point I toyed with the idea of selling complete packages and contacted several Chinese distributors to get quotes. On the lower end scales were around $150 for scales from the better brands (Ditron, Easson, etc.). The packages that you see for $300-$400 usually are sold under weird brands and I was told that those are factory rejects and the quality can be a bit or hit-or-miss. Some times they are rejected for cosmetic reasons, and some times the encoder strip doesn't pass the QA. 
At some point I ordered a "Jing" scale to test. It seemed to be OK but unlike my Easson scales that had the heads fixed for shipping with plastic brackets, the scale I got was held together with rubber bands. It also ended up being "single ended" (no differential signal), which is not a big deal, but it was mis-advertised and TIA/EIA-422. I mapped it over the whole length and the encoder strip is mostly within the spec except one spot where it had 3 missing "ticks" (0.0006" error). 
I paid $380 for three Easson scales IIRC (after some shipping around). On the lathe I use one 1um Ditron scale that set me back $180 on eBay and a magnetic scale on the Z axis. I had the Easson scales laser-calibrated (mapped) ant one point and they were *extremely* accurate, well within the spec and dead-nuts at 5080 pulses per inch. Jino ended up at 5096 pulses on one side and 5082 on the other (I did the calibration procedure on both ends to compare). Ditron scale was within the spec but with uniform 5084 pulses throughout the whole length. 
I would opt for Ditron or Easson because I have a bit of OCD and low-quality stuff drives me nuts, but they are a bit more pricey. I suspect the drop in quality from those to the non-name scales is much less than the drop in price. Plus, TouchDRO has linear error correction, so if the encoder is uniformly off, and in practice, unless you are some for of ninja, you won't be able to take advantage of 0.0002" resolution anyway on a milling machine, and a few thenths off is not a big deal.

Hope this helps.
Thank you
Yuriy