A power drill is a handheld or mounted tool that employs a motor to rotate a tool, typically a drill bit used to remove material from a workpiece or surface by leaving a hole of the desired shape and depth, or a large variety of sanding drums, circle cutters, gouges, polishers, chisels, etc. Power drills are extremely popular tools due to their great versatility and usefulness. The most common drill bit is the twist drill bit, which employs the mechanical principle of one of mankind's simplest machines, the Archimedean screw, to cut and lift material away from the workpiece or surface.
Types of drills
Homeowners, amateur woodworkers, and those requiring a useful but portable tool favor a handheld power drill consisting of a plastic handle and carriage housing an adjustable speed electric motor attached to a chuck, which holds the tool to be rotated. Handheld power drills can be corded or cordless and have simple direct drives or more complex clutches that permit the operator to set a torque beyond which the chuck will no longer spin.
Manufacturing and woodworking applications may require a drill press, which adds to the functionality of a handheld power drill by providing a much more powerful belt-drive motor, an adjustable work table, higher precision and reproducibility, and ease of use. Depth is controlled by a rack and pinion mechanism operated with a handwheel or lever that permits the operator to lower the chuck and bit into the workpiece with much less effort than would be required with a hand drill, which operates solely on muscle power and body weight and can be dangerous with operating against very hard materials like metals or masonry. Drill presses also have work tables that are adjustable in two dimensions and accommodate jigs, mounts, and clamps such that the operator can set and reproduce a variety of angles.
Hammer drills are used for drilling masonry and stone. They can be operated on the same principle as handheld drills by rotating a cutting bit into a surface in order to remove material. They can be also operated with or without a hammering mechanism that pulls the bit or entire chuck mechanism back and forth at up to 46,000 blows per minute (BPM's) in order to shatter and loosen hard materials like concrete, masonry, and stone. Hammer drills have substantially stronger carbide-steel chucks, side handles for good leverage, and heavier duty electric motors than their consumer grade counterparts. An 18 volt Makita cordless hand drill weights 4.2 lbs. A corded Makita hammer drill weighs 6.4 lbs.
Manufacturers of Power Drills
The most famous Power Drill company is arguably Black and Becker. These drills became very popular, owing to their convenience.
Advantages of Power Drills over Standard Drills
The patented Black&Decker trigger-grip handle on most power drills makes for ease of drilling. This is significantly more efficient than 'winding' the old style drills. It also means the drill can be operated by one hand, although for safety it is often recommended to not use the hand for other tasks while drilling - the spare hand can be used to position and guide the drill.