Abstract: A hollow rotor shaft for use in a small twin spool gas turbine engine in which the hollow rotor shaft is assembled by welding two hollow shaft sections together to form the single shaft assembly. One of the hollow shaft sections includes a lip that functions to form a snug fit prior to welding and also functions as a weld filler material. The hollow shaft ends each include a hole to allow for pressure equalization during the welding process to prevent bulging of the hollow shaft. To ensure a full penetration weld, an orbital welding process is used while passing an insert gas such as argon through the hollow shaft to minimize the buildup of material on the inner surface of the weld from the welding process. The shaft ends are pre-heated prior to welding. An insert gas is passed through the inner surface of the shaft sections during welding to prevent buildup of material on the inner surface of the hollow rotor shaft.