I have a Jet 1642 and I use a Nova G3 with an insert that can be used for reversing. I can leave the set screw out if I am not doing any reversing right? I have forgotten to loosen it before starting to take chuck off....And of course left a nice little gash in spindle. Not bad enough to affect anything.. .Ughhhhhhhhhhh I bet no one else has done that !!