Acu-Rite scales?

For a milling machine you will probably want a sent of 5-micron scales all around. At this point you have two routes - for "brand-name" Chinese stuff (i.e. stuff that will have some sort of support, you can try DRO Pros). Glass scales that they sell are basically the same as every other run-of-the-mill glass scales, but you get pretty good support and warranty. The drawback is that you will be paying 2.5-3x the prices.
The other option is pretty much the cheapest glass scales you can find on Amazon, eBay, etc. as long as you can get the pinout from the seller. (Even that is not really required, it's easy to reverse-engineer the pinout, and at this point 90% of Chinese scales have the same pinout anyway). The difference between "expensive" stuff and "cheap" stuff is quality control. The more you pay, the less likely you are to get a dead scale. Other than that, the "guts" are identical for the most part.

If you have an axis where you can't fathom loosing 1" of travel (or simply can't fit a glass scale), magnetic scales are a good option. "Micron-for-micron" and "quality-for-quality", expect to pay 2x+ the price. In this case you are paying the premium for compact size and the ability to cut down the scales [without giving yourself an aneurism***]. I've used Chinese scales before and they held up OK. One problem I ran into with them was that Ditron (at that time) used wrong 3M tape, which over time fell off (I use WD40 for aluminum cutting, and it destroyed the adhesion). The fix was to get the right 3M tape and re-apply the strip. A few months ago I took off that scale (I was using it for the X axis of my mill) and replaced it with a 24-inch (cut down to 22.75"). In theory I lost 1" of travel, but on my mill I don't remember ever pushing it that far.

For my lathes I prefer to have 1-micron scales on the cross slide. Since I want to show diameter, not radius for the X axis, 5-micron scale gives 10 micron resolution (0.0004" vs. 0.0002). One might argue that "who cares, 0.0004 is still pretty good", but it doesn't hurt. For the long axis (Z) a 5-micron glass scale is more than adequate.

I got EMS 1-micron scale from DRO Pros mostly because Chinese 1-micron scales are not that much cheaper, plus I needed a photo model for the blog :) The frame is way too big for my installation, so I ended up getting a strip of Ditron encoder tape and will machine a slimmer frame (the tape works fine, since the pitch is the same).

My setups as of today:
  • 2410 Jet Lathe - 5-micron no-name scale on the Z axis and 1-micron Ditron Slimline scale on X (this lathe is gettin a cleanup soon and will be looking for a better home, in case you wonder why one would have two 10-ish inch lathes)
  • 11" Rockwell - 5-micron no-name scale on Z, 1-micron EMS on X
  • SIEX SX4 mill - 5 micron Easson scales on Y and Z (the very first scales that I bough 10-ish years ago) and a new no-name scale on X. Quill will be getting the magnetic scale that used to be on the X axis (Ditron something-something 500)
  • Surface grinder - 1 micron scale on the column (no-name Chinese), waiting for another 1-micron scale on the Z axis.
  • SawStop cabinet saw - 1 micron Chinese scales... OK, kidding about this one :)

Hope this helps
Regards
Yuriy

*** I have cut down glass scales twice, and was successful both times, but it's pretty stressful exercise. For magnetic scales you just grab an angle grinder or a hacksaw ...
 
Thanks for the rundown on current state of scale choice.
Definitely helps! Thanks!
 
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