Attachment for machine tool

An attachment for a machine tool, which is detachably attached to a nose of a main spindle of the machine tool, comprising:

• an internal rotary shaft to which a revolution of the main spindle is transmitted;
• an external rotary shaft, arranged coaxially with the internal rotary shaft, for revolvably supporting the internal rotary shaft in its center hole,
• a main body for revolvably supporting the internal and external rotary shafts;
• an attachment main spindle, arranged in a direction which crosses over the axis of the internal rotary shaft, revolvably driven by a revolution of the internal rotary shaft, and a tool being detachably attached to a nose of the attachment main spindle;
• a swivel part for revolvably supporting the attachment main spindle, the swivel part being swiveled by the revolutions of the internal and external rotary shafts,
• indexing means for enabling the main body and the swivel part to be disengageably engaged with each other, and thus for enabling swiveling the swivel part relative to the main body for indexation;
• traveling means for traveling the internal and external rotary shafts in their respective axial directions;
• restricting means for restricting the revolution of the external rotary shaft when the traveling means travels the internal and external rotary shafts to a first side with the indexing means engaging;
• and
• connecting means for connecting the internal and external rotary shafts to each other when the indexing means disengages after the traveling means travels the internal and external rotary shafts to a second side, wherein
• when the internal and external rotary shafts travel from the first side to the second side, the restricting means stops restricting the external rotary shaft after the internal and external rotary shafts are connected to each other by the connecting means.