A ceiling fan may be making a grinding noise because it has unbalanced blades that are causing the fan to wobble. Ceiling fan blades can become unbalanced by dust collecting on the blades when the fan isn't in use. Therefore, it is important to clean them frequently by wiping them down with a damp rag to remove any dust and debris causing them to be unbalanced. You may also need to detach the blades to realign them. To do so apply pressure while bending them so that you can bring them back to their original shape.