I just sent off an e-mail to the guys at DRO Pros to see if their head units might be compatible with my Mitutoyo AT102 scales. I'd not be able to afford to put new scales on and can't justify the cost and time because it's so hard to get to the back side of my lathe. I had to do that once already with the 800mm scale for the Z axis.

Back a few years ago, shortly after I got him the machine, my dad and I added a Royal Machine 5C lever type collect closer. Prior to having that, the original POS 3-jaw chuck had lived on the machine and was never (to my knowledge) changed. Now with the collet closer the carriage could be cranked all the way in to the stop at the head end. With a 10" 3-jaw chuck, it stopped at least 4-1/2" (115mm) away.

Unbeknownst to us, the 800mm scale was never installed correctly. It had been mounted too far to the right (tailstock) end of the machine by about 4". As such, the reader head could never touch it's end of travel to the right, but because we can't see it from the operator position, cranking the carriage up close to a collet knocked it out of position. The reader head's bracket that reaches up into the housing to put the reader on the glass scale wore right through and eventually broke off. No wonder the Z axis readout "froze". I bought a "new old stock" 100mm long AT102 scale off eBay for short money and used it's reader head to fix my machine. It still works perfect, because I shifted the mounting of the 800mm scale to the proper position and realigned it. Now it's in the "safe zone" at both ends of the total travel of the carriage.

While I want a DRO on the machine that can be pre-set to a given diameter and length, plus use tool offsets, I hate to spend extra money for scales when I have two perfectly functional glass scales already installed.