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 D1 to D11. The corresponding positions of C are C1 and C11 as shown in the fig. 1.38. For the point C to move from C1 to C11, point B moves from B1 to B11, in anti-clockwise direction. I.E., cutting stroke takes place when input link moves through angle B1O2B11 in anti-clockwise direction and return stroke takes place when input link moves through angle B11O2B1 in anti-clockwise direction.

Fig.1.38 The time ratio is given by the following equation.

Timeforforwardstroke Boˆ2 B 1 Timeforreturnstroke Boˆ2 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 D1 to D11. The corresponding positions of C are C1 and C11 as shown in the fig. 1.39. For the point C to move from C1 to C11, point B moves from B1 to B11, in anti-clockwise direction. I.E., cutting stroke takes place when input link moves through angle B1O2B11 in anti-clockwise direction and return stroke takes place when input link moves through angle B11O2B1 in anti-clockwise direction.

Fig.1.39 The time ratio is given by the following equation.

Timeforforwardstroke Boˆ2 B 1 Timeforreturnstroke Boˆ2 B 2