Whitworth quick return motion mechanism: This is first inversion of slider mechanism, where, crank 1 is fixed. Input is given to link 2, which moves at constant speed. Point C of the mechanism is connected to the tool post D of the machine. During cutting stroke, tool post moves from D 1 to D 11 . The corresponding positions of C are C 1 and C 11 as shown in the fig. 1.38. For the point C to move from C 1 to C 11 , point B moves from B 1 to B 11 , in anti-clockwise direction. I.E., cutting stroke takes place when input link moves through angle B 1 O 2 B 11 in anti- clockwise direction and return stroke takes place when input link moves through angle B 11 O 2 B 1 in anti-clockwise direction. Fig.1.38 The time ratio is given by the following equation. Timeforforwardstroke Boˆ 2 B 1 Timeforreturnstroke Boˆ 2 B 2 Crank and slotted lever quick return motion mechanism This is second inversion of slider mechanism, where, connecting rod is fixed. Input is given to link 2, which moves at constant speed. Point C of the mechanism is connected to the tool post D of the machine. During cutting stroke, tool post moves from D 1 to D 11 . The corresponding positions of C are C 1 and C 11 as shown in the fig. 1.39. For the point C to move from C 1 to C 11 , point B moves from B 1 to B 11 , in anti-clockwise direction. I.E., cutting stroke takes place when input link moves through angle B 1 O 2 B 11 in anti- clockwise direction and return stroke takes place when input link moves through angle B 11 O 2 B 1 in anti-clockwise direction.