The PLEK can be used on just the nut.
It could never get a nice finish on the fingerboard. If it cut the radius on the board it would still have to be hand finished.
Yes. The PLEK job on my Conklin did a fantastic job cutting the nut. But the luthier who owned the PLEK machine used a Dremel and tiny buffing wheel to put the final finish on the cut frets. Bass did come away absolutely amazing.
