A robotic welding system comprises a supporting arm for attaching to a repositionable support structure, the supporting arm comprising a first mounting portion connectable to the repositionable support structure, and a second mounting portion rotatably coupled to the first mounting portion. A yaw rotary actuator rotates the second mounting portion about a yaw axis. A welding arm comprises a third mounting portion rotatably coupled to the second mounting portion of the supporting arm. A pitch rotary actuator rotates the third mounting portion about a pitch axis generally perpendicular to the yaw axis. A roll rotary actuator rotates a torch holder shaft about a roll axis generally perpendicular to the pitch axis. The shaft has a torch mounting portion for mounting a welding torch at an end thereof. A controller is operably coupled to the actuators to cause the welding torch to execute a welding pattern.