If impact is used to remove screws or nuts, the motor bearings can be damaged :
Brinelling is caused when a load is applied to a ball bearing that exceeds the elastic limits of the steel and the raceways are permanently deformed. Brinelling creates measurable dents at each ball location similar to the deformation caused by a Brinell Hardness Tester. This type of damage can occur quite easily if proper care is not taken. High energy impacts (from hammers and smash-ups), improper bearing handling and incorrect spindle assembly can all damage bearings. Remember that we are talking about bearings with raceways with roundness measured in millionths of an inch. Damage may result in increased vibration and non-repetitive run-out.
To determine carrier lock nut thread :
When viewed from the side, if the burr carrier thread rises from left to right, it's right hand. If it rises from right to left, it's left hand.
Looking at the end of the bolt, if the thread drops away in a clockwise direction, it's right hand. If it drops away counter-clockwise, it's left hand.
Grinders are one of the keys to exceptional espresso. Discuss them here.