Reamers and Broaches

Broaches are used to gently enlarge and smooth holes with great precision. Cutting broaches are used to enlarge the hole to a precise size after it's been drilled, while smoothing broaches enable you to burnish the hole to reduce wear on any moving parts which will pass through it. Reamers are used to enlarge previously drilled holes; using files for this is tempting, but the result will normally be oval rather than circular, whereas reaming a hole out correctly will retain the circular shape.