Managed to get full speed control via my speed pot on my control box up to 400Hz.
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I needed to alter another setting on the vfd. I also have start/stop control working via USBCNC now as well. All I need to do is manually select the Coolant flow icon on USBCNC first then the program will start and stop the VFD.:dance:

What I need to do now is calibrate the travel distance of my Z axis and then I should be ready for a test cut.

Ian