A reamer is a type of rotary cutting tool used in metalworking to enlarge the size of a previously formed hole by a small amount but with a high degree of accuracy to leave smooth sides
. Reamers are used to finish holes that have been drilled, end-milled, or punched, leaving them with very accurate dimensions
. They are designed to produce smooth and precisely round holes of very high diametral accuracy and cannot create a hole where there is none; reamers can only expand an existing hole by up to 10%
. Reamers are used to remove small amounts of material and correct holes that are imperfectly rounded or not quite straight
. They are available in a variety of shank styles that can be mounted into hand tools, chucks, collets, or other tool holders, and are used in a variety of portable or stationary machines such as drill presses, lathes, screw machines, milling machines, and more
