Hey buzzfab,
good suggestion. Having a sensor that detects spindle coolant flow is important. If you just have a dumb flow indicator you have to look at the machine all the time.
The cooling station I own has this already integrated. It sends an alarm if coolant flow or temperature have bad values:
Image: Alarm connector socket for flow and temperature alarm on cooling station Mechatron KG5000
Nice video. You explain every step very nicely.
Just one thing: When you solder two wire ends together, you normally twist the wires first, then add solder paste and only then solder. The reason for this is that this way the wires are not only connected by the solder, but also mechanically by the twisting. It is assumed that a connection must still hold if the solder melts (e.g. due to a short circuit). In this low-voltage application, this does not matter, but it is good practice.
– Image source: Wikihow: Kabel zusammenlöten