The instruction page for the tool is not very good. And you must be careful to follow the blade alignment pattern. My blades were installed as NO-NO as stated in the instructions. The instructions don't say anything about the two screws on the outside of the bar that hold the blades, but I learned about them quickly. If the screws are not tightened (they don't seem to do anything - I don't know why they are there) they will loosen during operation and start rubbing against the inside of the plastic casing, disrupting the tool's operation. It took me 2 full holes to figure out what was going on before taking it apart and tightening the screws with a screwdriver. Another thing is speed. I drilled 6" holes and if I cranked it up too fast, dust would start flying out of the hood. You have to keep a moderate speed and hardly any dust comes out. Drilled 10 holes in 3/4" drywall with no problems. DEFINITELY worth the money.