A portable rail weld milling machine apparatus comprises a metal frame that incorporates a motor with a rotary carbide tool that is able to lock to a rail or rails for stability. The apparatus houses the required guides and motors to maneuver the tool on a plurality of axes with computer numerical control (“CNC”). The CNC programming is able to control the carbide tool such that the welded rail can be milled to proper profile on the entire running surface, including the top, the field side, and the gauge side of the ball of the rail.