"...but you drill the hole with the drill and then drive the screw with the impact driver, because it's *enormously* more effective at driving screws than a drill or even a hammer drill - the mechanism has been designed for that. That's why when you go to buy a battery powered drill, it's very often sold in a pack of two tools - a drill/driver and an impact driver. And it's as fast as using this drill bit, if not faster because while you have to reach to your toolbelt for the impact driver, it drives so much faster than the drill that it more than makes up for the time."