Unclamping arm and machine tool

An unclamping arm, rotatably supported within a spindle head of a machine tool which comprises:

• a spindle on which a tool is to be mounted, a tool gripping mechanism provided inside the spindle and configured to fix or release the tool to and from the spindle, the spindle head that rotatably holds the spindle, and an upright column that movably supports the spindle head, and configured to operate fixing or releasing of the tool by the tool gripping mechanism, the unclamping arm comprising:
• a fulcrum section rotatably supported within the spindle head;
• a force point section, in conjunction with a movement of the spindle head, configured to come into contact with a contact section provided on the upright column and receive an external pressure;
• and
• an action point section configured to, by the force point section rotating about the fulcrum section upon receiving the external pressure, press or not press the tool gripping mechanism to operate fixing or releasing of the tool by the gripping mechanism,
• wherein the action point section is located between the fulcrum section and the force point section,
• the fulcrum section and the action point section are located on a straight line intersecting an axial direction of the spindle, and
• the force point section is located at a position away from the fulcrum section toward a side of the upright column.