I've now completed by the CNC conversion of my Optimum BF30 and its time to build a high speed spindle so that I can use small cutters / engraving bits.
The concept is to follow on from the success of others and build the spindle around an RC BLDC motor with an 8mm shaft, an ER11 collet chuck with an 8mm parallel shank, some angular contact magneto-bearings. For controllers I'll use RC testers to start with but may connect up to LinuxCNC later.
The body of the spindle will be chopped out of 1.5" dia steel bar.