Automatic unpowered opening and closing grinding tool turning angle system

According to the automatic unpowered opening and closing grinding tool corner turning system, a corner turning mechanism is connected with a mold bottom mold, a pair of corner turning bases are fixed to the mold bottom mold, a corner turning rotating shaft is rotatably connected with the pair of corner turning bases, a mold corner turning is fixedly connected to the middle of the corner turning rotating shaft, and a pair of balance weights are connected to the two ends of the corner turning rotating shaft; the pair of closed pressing rods is connected to the two ends of the corner turning rotating shaft. The closed pressing rods and the balance weight are located on the two sides of the corner turning rotating shaft. The pair of elastic ejector rod mechanisms is arranged in the mold middle mold, the mold middle mold is arranged on the mold bottom mold in a liftable mode, the elastic ejector rod base is fixed to the mold middle mold and located above the closed pressing rod, the elastic ejector rod barrel is v