Question::
If you have a horizontal mill and add the vertical mill head, does that change the name of the travel directions?
So:: horizontal mill:: up/down = Y :: in-out = Z :: left-right = X
in Vertical config:::: up/down = Z :: in-out = X :: left-right = Y
Does anyone change their DRO readouts to correspond ?
On manual equipment it doesn't make any difference. You could call them ed, bob and Steve, and get the same results.
It's just that in certain industries, people get into the habit of following certain rules, and carry it over to their personal hobby stuff too. Like when your wife tells you the helicopter light came on in the car. If your a car guy, your first thought Is "huh!?" but there are likely plenty of husband's out there who'd totally understand the reference. And if you both know what she's talking about, does it really matter which word she picks to describe it.
The helicopter light:
Like "drill bits", or the "motor" in a car and and a ton of other terms that are normal to most. It only bugs a small subset of people who work in those specific industries, and have either formal education or have ingrained habits regarding terminology rules.
GD&T terminology gets alot of machinists and Engineers rolling their eyes, probably the same way infantry soldiers would roll their eyes when the engineer describes how to put a clip in his gun and cock it.
On CNC equipment, you wouldn't want a program with 100,000 plus lines of software generated code sending x, y and z commands to the wrong servo motors.
If a guy is using a cnc vertical mill, and swaps to a horizontal spindle, he would need to set his cam software up to generate the correct commands to the correct servo drivers, and that would likely also involve change the designations in his cnc motion control software. I only have a vertical spindle on my cnc mill, but I could reassign the axis designations in about 30 seconds if needed.
As to manual equipment. I just refer to each axis as my training and experience justify. It helps me avoid mistakes.
But, if someone asks, I like to answer with correct textbook answers. It's not meant to imply that anyone should change the way they do things.