Electron Beam Welding is a method which uses a focussed stream of high energy electrons generated by a filament and directed to the joint requiring to be welded. The heating is very localised and the bulk of the assembly therefore remains cold and stable. This results in a very narrow weld with a minimal heat affected zone. There is no need to use filler metal as the parent metal of the assembly is melted. As this is a line of sight method it is not possible to weld around corners or re-entrant angles. Weld depths of up to 30mm can be produced and computer controls ensure minimal operator dependence, thus providing good reproducibility throughout a batch of components, even though this is a piece part process. Since the heat input is very localised it is possible to weld together previously heat treated components, which is a very economical method for producing composite gear shafts, with for example a case hardened gear on a hardened and tempered shaft.