Mandrel and saw are slightly uneven which means they will not cut perfect holes. To an extent, I solved this problem by clamping a piece of wood under the piece I was drilling, which generally held the drill bit in place fairly well and produced an acceptable hole. Not a bad set for the price, but not great either. It cuts holes easier than by hand. it was what i needed. It should also work reasonably well in a drill if you happen to have one of those horns laying around. Be warned though: unless you're clamping a piece of wood under what you're sawing (or alternatively use a drill press). You will most likely get a hole and ruin your work piece.