Abstract: Dust-pressed plates (P) are trimmed to a predetermined peripheral profile by means of three milling cutters rotating at around 12,000 r.p.m. The cutters are uniformly spaced about a central axis and operate simultaneously on the periphery of a plate while the plate is rotated about the axis. The cutters are located during trimming by means of a profile cam which is in registration with the plate mounted on a ware support. To ensure registration with the cam, a plate is centered by a centering unit before being orientated by orientating mechanism and transferred to the ware support. Each plate is delivered to the centering unit with a reference feature at a predetermined position on its periphery, the orientating mechanism being arranged to search for that feature before rotating the plate to bring it into the required orientation for registration with the cam.