Proxxon MF-70 brushless motor coupling

I accidentally burnt out the spindle motor on my mf-70 recently while milling steel (Not v impressed at quality, it stalled, spat out some smoke then died). I had a spare turnigy 2217 860kv 22A motor from my quadcopter, so decided to replace the stock brushed motor with this much nicer brushless one. This part clicks into the spinning body of the motor, and has a hole for the stock rubber coupling. I was thinking I'd immediately mill a metal part for increased strength, but this seems to be fine