Abstract: Embodiments of the invention relate a valve fitting milling system and method for use with transmission pipes. One embodiment relates to a milling adaptor used with a valve housing having a temporary gate extending about the pipe and a mill. The milling adaptor includes a main adaptor plate removeably connected to the valve housing which defines at least one milling slot; a sliding gate cutting adaptor movably contacts the main adapted plate and defines at least one cutting hole; a cranking rod engages the sliding gate cutting adaptor and moves the sliding gate cutting adaptor with respect to the main adaptor plate; and a top retainer track removable connected to at least the main adaptor plate. The mill engages at least the sliding gate adaptor and mills a cross-cut hole in the pipe to receive a valve therein.