Using current as cutting force indicator?

[Jonathan]

I'll play around a little to see what the no load current looks like at different frequencies and take it from there.

If you're keen you could take several readings, graph them then use that as a look-up table or function to subtract from the on-load current in software, on an Arduino (or similar), then connect a display... In fact you could do it quite easily with an Arduino, current sensor and display:

http://www.ebay.co.uk/itm/New-Blue-I...item3f3eb02c30

http://www.ebay.co.uk/itm/Range-ACS7...item565bbee604

The though had crossed my mind to put a thick glove on and gently apply pressure to the collet nut but I'm way too scared to be the first guy to try that :-)

You wouldn't be the first ;)

[mitchejc]

Arduino. Yep those are very high on my list of things to toy with, just wasn't sure what I'd use it for but now I have a plan!

Sorry last stupid question. Using this approach with that sensor would I measure current on then single phase input side of the vfd or on the output side or does it even matter?

[Jonathan]

Output side - you want the line current. You could use the current sensor to measure the frequency of the current, then scale that to read spindle speed... just for fun.