It was an easy enough install but you will need to make mounts for the new spindle to attach to the HEIZ. This is my effort:

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It's the 1.5Kw water cooled spindle that I bought with the body dia. of 65mm. I used a standard LPT cable for LPT2 and built a separate control panel.

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I bought a long ribbon cable extension for the VFD control panel and I have a manual potentiometer that I can switch to if I want to overide the commands from WinPCNC. Also included is a temperature controller which controls 4 PC fans that are mounted on a van heater matrix and the water flow is supplied by a fish tank pump. That's the LPT2 cable that you can see and then the internal electronics are tapped from that.