An air cycle machine includes a shaft formed from end sections attached to a center section. The center section includes a first diameter that is supported on bearings within the air cycle machine and a second diameter that forms a part of an interface with a corresponding end section. The second diameter is less than the first diameter and extends an axial distance from an end of the center section and provides for the weld beam to be directed normal to the interface location such that weld quality and manufacturing efficiencies are improved.