Remove the rubber sleeve from the neck of the die grinder 
Remove the 4 screws that hold the neck on 
set aside the plastic coupler & large washer 
While holding the neck in a vice, unscrew the collar nut 
Set aside the smaller washer & felt washer that were behind the collar nut 
Using the handle of the crescent wrench, unscrew the butterfly nut 
Set aside the butterfly nut 
Place new shaft in the neck. 
Place metal washer and felt washer into neck, then reinstall collar nut. 
Reinstall butterfly nut. Note the vice is holding the shaft 
Reinsert plastic coupler 
Place large washer in neck 
How it looks before reattaching the neck 
Reattach the neck with 4 screws, be careful to line up exhaust vents to the side 
Slide the rubber cover back onto the neck
