Drill

See also Drill (album) and drill (fabric).

A drill is a tool with a rotary drill bit used to bore holes through material. The twist drill is most common, consisting of a cylindrical metal rod with two helical "flutes" or grooves spiralling along its length. Straight flutes are also sometimes used. The drill bit is held by the drill at one end, with the other end being pressed against the target material and rotated. The earliest drills were probably bow drills.

The tip of the drill bit does the work of cutting into the target material, slicing off thin shavings or grinding off small particles. This debris is carried up and away from the tip of the drill by the fluting, falling out of the helical grooves once it has been lifted clear of the hole. Lubricants and coolants (i.e. cutting fluid) are also sometimes used, with the fluting providing channels for these as well.

A drill press is a drill mounted so that the drill can only move in the direction of the drill bit.

Drills are commonly used in woodworking. They are also useful for cutting holes for metalworking, especially softer metals such as iron. Straight fluting is used for copper or brass, exhibiting less tendancy to "dig in" to the sides of the hole than helical fluting. For heavy feeds and comparatively deep holes oil-hole drills can be used, with a lubricant being pumped to the drill head through a small hole in the bit and flowing out along the fluting. Oil-hole drilling can be used in a conventional drill press arrangement, but is more commonly seen in automatic drilling machinery in which it is the workpiece that rotates rather than the drill bit.