An acetabular reamer, i.e. rotary cutter, comprises a hemispherical shaped head 2 provided with a plurality of blades 5 mounted therein the blades 5 preferably being secured to the head by means of securement means 14 interacting with an inner surface of the head 2. It is preferable that the head 2 be formed as a single unit, perhaps through 3D printing, and that the blades 5 be separable from the head 2 such that they may be disposed of after use. The securement means provided on the blades preferably comprises a projection 14 which extends to the inside of the head 2 and is bent over to secure the blades 5 in position. In order to secure the blades 5 to the head 2, the head 2, with blades 5 placed therein, may be placed in a concave hemispherical shaped block [23, Fig 14] and a paddle [25, Fig 14] inserted into the hollow of the head 2 and rotated to bend each of the projections 14 provided on the blades 5 to secure the blades 5 in position on the head 2.
