The blade is right hand threaded onto the motor shaft. If the motor is running, I can't understand why the blade is stationary unless the threads are stripped. That would seem unlikely though. If you are trying to remove the blade by twisting the blade's plastic hub, it probably will break before the blade is loosened. (Have you have removed the bottom of the grinder to access the slot in the end of the motor shaft ?) By inserting a screwdriver in the slot you can keep the armature stationary while you unscrew the blade. Then (with a rag for padding) the blade can be unscrewed (with a bit of effort). If the armature isn't turning when you are trying to remove the blade (and you haven't removed the base to access the slot), then the motor is probably frozen. Time to spend $20 on a new grinder. Also, even if you get it apart, I don't think there are any serviceable parts inside.