Tried these for the first time today, couldn't even drill through the piece of plywood I was attaching thinking it might be a knot or something in plywood, tried in scrap piece of pine 2x4. no-go Upon closer inspection, it turned out that these things weren't even sharpened. All of them. the cutting edges of the countersinks were simply flat, without cutting edge angles, the drills had a point, but they didn't drill anything either. Unusable set, returned for a refund.