just flicking spindle on and off with a relay

[irving2008]

As Jonathan said, you need to find the 'Run' input on your VFD. What model is it?
You shouldn't really switch supply volts to a VFD.

right... Im now able to turn on 5v and turn off 5v to a pin, by running the m3 command etc.. however it seems there is not sufficient power to pull a relay.... therefore... how do I get from the 5v signal... to flicking the spindle vfd on and off?

i assume an opto coupler?

[birchy]

As mentioned above, most VFD's only require a N.O. contact between 2 pins to trigger the start/run signal, so you'll have to use a switching circuit such as a miniature relay or a semiconductor (transistor, etc).