- " I personally prefer to always be conscious and careful, and not get dependent on external devices"
- " I still stand by the old habit of turning the chuck, faceplate, or drive dog at least one full turn by hand before starting the lathe."
It's OK not to trust any 'external device' they are méchanical per definition so a contact can come out lose, a screw missing etc...
THEY WILL FAIL ONE DAY OR ANOTHER this is why verifying this sort of things should be included in your routine maintenance.
BUT!
The good safety habit you seems to have acquired, as fine as they are, YOU WILL FORGET IT ONE DAY OR ANOTHER! I can guaranty this also.
And that single omission, because you are tired, stressed by production schedule or whatever reason, may hurt you.
So we need absolutely both: acquire the proper habits and reflexes, and install, inspect and maintain a good safety interlock system.
On each machine! The chances that one get distraught and experience a failure of a safety mechanism then becomes about null!
And don't completely trust one or the other, in other words, be weary! I never stand directly in front of the chuck when I start the machine, I never stand in front of the main breaker switch on a new installation and I turn my head away while doing so, wearing leather gloves that goes up to my elbow (here in Canada, our industrial power is 600Vac/3 phases, when you make a wiring mistake, that switch will bark at you in a ferocious display of flames, smoke and explosion! No joke!
Luc
PS: it is a simple matter to make a two chuck keys holder with microswitches in the safety loop... Come on do it!