Hi
If you look at attached for MACH4, it is possible to use check FEED HOLD to stop Spindle and exiting FEED HOLD restores Spindle.
Now a VFD driver usually has an output relay so that when spindle is spinning that output relay can turn on coolant. So when the spindle stops spinning, the coolant would be off too.
Also in the second attachment, there are already buttons to manually turn off/on coolants too.
I know people like programming, I was an IBM MVS Cobol, CICS programmer long time ago. And I know LUA since more than 10 years ago.
BUT why do things that to me are superfluous yet seemingly so difficult to many?
It could only put off more hobbyist from buying MACH4.