Abstract: A rotary cutter (A) adapted to open a pre-drilled hole to a larger diameter, comprises a shank (3) of industry-standard external profile adapted to fit into a chuck, arbor, etc of a drilling machine, a co-axial cutting section (5) extending from the shank (3) and a co-axial, non-cutting pilot boss (9) extending from the cutting section (5), the latter being of the required larger diameter (D) for the pre-drilled hole, and the pilot boss (9) being of smaller diameter (d) and, hence, undersize with respect to the pre-drilled hole.