I have a (very nice) Chi-wanese step-pulley BP clone that has a rattle in the head. I've had it apart more times than I can count, and am stumped. All bearings are tight, nothing seems at all wrong anywhere. The rattle occurs primarily when doing side-milling with 2-flute EMs, or when coasting down to rest from high speed (I run up to 8200 RPM on the spindle). I've removed the toothed belt, to ensure the noise can't be coming from the backgears. So, I'm down to only two possibilities I can see - either the dog drive, or the splines between the spindle and bull gear. It does seem to lessen if I pack grease into the spindle bore, which suggests the splines are the problem. Anyone have any ideas what I can do about this, other than getting a new bullgear and spindle, and hoping for a better fit? Any other possible noise sources I should be aware of?
BTW - Since the machine is CNC'd, the head has been pretty much stripped of all non-essentials - the quill drive and all quill pinion hardware have been removed.