Abstract: An arbor 1 having an axis of rotation 2 comprises a body member 3 having end 4 with flats so that it may be drivably secured in a spindle or chuck of a machine or machine tool. The body member 3 has a co-axial socket 5 provided at its opposite, cutting end 6 to receive a shank of a rotary cutter (not shown), the shank having, in the conventional manner, at least one flat. The arbor 1, further comprises a collar 7 carried at the cutting end 6, which collar 7 is biassed by a torsion spring 8 to an active position and is manually rotatable, within limits, against the spring bias, to an inactive position.

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.