Let the fun begin !!! ???

[JAZZCNC]

Don't what ever you do put anything between the VFD and spindle to break the circuit ie: Contactor or relay. You will damage the VFD and Spindle.

If you want to play on the safe side then put the VFD power on a timer relay and put this in series with the E-stop.
The E-stop signal back to the control will switch off the Spindle in software when it see's E-stop or put the Run signal from vfd thru NO contact on your E-stop relay for safe measure so not relying on software. The Timer relay will allow time for the spindle to coast to a stop before dropping power to the VFD.
This is the safest way.

Personaly I'm ok with Just putting Run signal thru E-stop contact or Relay in series and leaving VFD under power. I Never leave turning off anything to Software.

Regards the Water pump I bought last ones off Ebay and they where about £15. Can't remember seller name, it was China Job but if get chance I'll take a look.