Rotational force transmission mechanism, turret tool rest, and lathe

A turret tool rest comprising:

• a turret which is swingable about a second axis and on which a plurality of tool holders are mountable;
• a shaft contained in the turret rotatably about a first axis, the shaft including a leading end portion having a second groove and a first groove which is configured to receive a rotatable portion of a tool holder that is among the plurality of tool holders and that is disposed on the first axis;
• an engagement pin provided in the shaft to move along the first axis between a first position and a second position and to rotate about the first axis together with the shaft, the engagement pin including an engagement portion which is received in the second groove;
• and
• at least one of the shaft and the engagement pin having an inclined surface that moves the engagement portion in a direction toward the first axis when the engagement pin moves from the first position to the second position so that, in the first position, the engagement portion does not engage with the rotatable portion of the tool holder and rotational force is transmitted from the shaft to the rotatable portion without via the engagement pin and so that, in the second position, the engagement portion engages with the rotatable portion to transmit the rotational force via the engagement portion.

A lathe comprising:

• a base;
• a spindle configured to support a workpiece;
• a turret tool rest comprising:
• a turret base;
• a turret which is swingable about a second axis and on which a plurality of tool holders are mountable;
• a turret actuator configured to swing the turret about the second axis;
• a shaft contained in the turret rotatably about a first axis, the shaft including a leading end portion having a second groove and a first groove which is configured to receive a rotatable portion of a tool holder that is among the plurality of tool holders and that is disposed on the first axis;
• a shaft motor configured to rotate the shaft about the first axis;
• an engagement pin provided in the shaft to move along the first axis between a first position and a second position and to rotate about the first axis together with the shaft, the engagement pin including an engagement portion which is received in the second groove;
• at least one of the shaft and the engagement pin having an inclined surface that moves the engagement portion in a direction toward the first axis when the engagement pin moves from the first position to the second position so that, in the first position, the engagement portion does not engage with the rotatable portion of the tool holder and rotational force is transmitted from the shaft to the rotatable portion without via the engagement pin and so that, in the second position, the engagement portion engages with the rotatable portion to transmit the rotational force via the engagement portion;
• and
• an engagement pin actuator configured to move the engagement pin along the first axis;
• and
• a carriage configured to move the turret tool rest relative to the base.