Patent ID: 8657541

Claim:
A spindle head for a machine tool, the spindle head including a main shaft ( 9 ) that rotatably supports a spindle ( 10 ) to which a tool is mounted; a pair of support shafts ( 58 , 59 ) including coaxial axial lines which intersect the main shaft ( 9 ), the pair of support shafts ( 58 , 59 ) being provided on respective sides of the main shaft ( 9 ) and being secured to the main shaft ( 9 ); a frame ( 4 ) that rotatably supports the pair of support shafts ( 58 , 59 ); and a rotation driving device ( 56 ) for at least one of the pair of support shafts ( 58 , 59 ), in which the spindle ( 10 ) is rotated around the axial lines of the support shafts ( 58 , 59 ) by the rotation driving device ( 56 ), wherein two rotating members ( 9 , 58 ) that form a rotation transmission mechanism for rotating the spindle ( 10 ) and that transmit drive force of the rotation driving device ( 56 ) are fastened to each other at respective connection sections thereof by a bolt group ( 301 ) and are connected to each other so as to be prevented from rotating relative to each other by friction force resulting from the fastening, and wherein rotation prevention torque based on the friction force is a value greater than torque applied to the connection sections during processing and smaller than torque applied to the connection sections when external force that causes the spindle ( 10 ) to deform beyond a permissible range during the rotation of the spindle ( 10 ) is applied to the spindle ( 10 ).