Chap, 5.2 The fundamental law of gearing(s) 了3. Pressure angle(节圆压力角) Driving r The pressure angle in a gearset defined as the angle between the axis of transmission or line of action (common normal) and the direction of velocity at the pitch point. n r Meshing angle(啮合角) r Standard value of the pressure angle are 1450 200 and 250. 200 is the most commonly usedChap.5.2 The fundamental law of gearing(8) 3. Pressure angle（节圆压力角） The pressure angle in a gearset is defined as the angle between the axis of transmission or line of action(common normal) and the direction of velocity at the pitch point. Standard value of the pressure angle are 14.50, 200 and 250. 200 is the most commonly used. Meshing angle(啮合角)