Reaming

Reaming is a precision finishing operation that uses a multi-flute reamer to enlarge a pre-drilled hole to an exact, tight-tolerance diameter, improving roundness, straightness, and surface finish far beyond what drilling alone can achieve. A reamer follows the path established by the pilot hole (usually created by a drill), so reaming does not correct for mis-drilled holes but instead produces a precisely sized, smooth-walled hole ideal for close-fitting pins, bushings, or bearings.

CNC machining centers often perform reaming immediately after drilling in the same setup, minimizing part handling and ensuring hole concentricity to the reference surface. Reamers are available in numerous sizes (fractional, metric, and decimal), and the choice of reamer material (high-speed steel, carbide) and coatings affects tool life and surface finish.

For high-precision applications requiring hole tolerances of ±0.0005 inches or tighter, reaming followed by hand reaming or honing may be necessary to achieve the required accuracy and finish.