L-shaped composite ring groove cutting tool

The invention provides an L-shaped composite ring groove cutting tool and a cutting machining method thereof. The cutting tool comprises a tool bar, a blade and a pressing plate, wherein one end of the tool bar serves as a tool bit; the pressing plate is fixedly connected with the tool bit through a bolt; the blade is clamped between the pressing plate and the tool bit; an arc-shaped front cuttingedge and an arc-shaped rear cutting edge are arranged on the front side and the rear side of the blade correspondingly; a pair of parallel flat auxiliary cutting edges is arranged on the left side and the right side of the blade; the left side and the right side of the front cutting edge are connected with the left side and the right side of the rear cutting edge through the auxiliary cutting edges to form a closed annular composite cutting edge; and the cutting machining method comprises the steps that firstly, a square-head tool and a round-head tool are used for machining an outer sinkinggroove; and then the cutti