Abstract: A metal matrix composite component e.g. a brake disc, is provided with a protective coating to prevent displacement of the reinforcing filler in the matrix when the component is placed under load. Preferably the protective coating is metal, alloy, composite, refractory or ceramic applied e.g. by electro-plating.

Abstract: A method of making a threaded hole in a component includes the steps of inserting into a preformed hole a cold forming tool comprising spaced apart threaded forming rings, a main passage for the passage of fluid extending through the tool, and branch passages leading from the main passage to outlets between adjacent thread forming rings, and directing pressure resistant lubricant fluid to flow under pressure through the passages to the outlets between adjacent rings into a gap between the tool and the wall of the hole to be threaded to cause the threads to be formed by displacement and deformation of the component material by the pressurized fluid.