DeWalt DCF840B Impact Driver vs DEWALT 20V MAX Brushless Hammer Drill DCD999B

The DCF840B is the better pick if you drive screws all day: it is a compact 1/4 in. impact driver with 1,850 in-lb of torque, three speeds and a 2 lb body that fits into tight framing and cabinet work. The DCD999B is the better pick if you need one tool for drilling holes and driving fasteners: it is a 1/2 in. hammer drill with a keyless chuck, a 3-speed gearbox, 11 clutch settings and hammer mode for masonry. Owners of the DCF840B praise the power-to-size ratio and the three LED lights; owners of the DCD999B praise the flexibility but note it is longer and heavier, and hammer mode is slower than a dedicated rotary hammer.

• Choose the DCF840B if you mostly drive screws and want a short, light tool that reaches into tight spaces.
• Choose the DCD999B if you need to drill holes in wood, metal and masonry as well as drive screws with one tool.