Abstract: Improvements are provided in the method of manufacturing a ring-shaped part by machining a segment of vulcanized fibre tubing having a predetermined wall thickness and a waste portion adjacent one end of the segment. The wall thickness is reduced in an axially extended region of the waste portion that is spaced from the end of the segment, and a chucking lip, which projects above the adjacent surface of the reduced wall thickness region, is provided intermediate that region and the end of the segment. An annular stop shoulder is provided in the segment surface opposed to the surface which incorporates the chucking lip, whereby a floating mandrel may be positioned against the shoulder to provide support for the tube wall when it is clamped at the chucking lip.