MAIN SPINDLE COOLING CONSTRUCTION

PROBLEM TO BE SOLVED: To restrain twisted and irregular thermal deformation of a main spindle by providing a plurality of annular cooling grooves in parallel with each other on the outer circumferential face of the spindle head of a machine tool, and communicating together the cooling grooves by a plurality of communicating grooves in the axial direction. SOLUTION: Cooling grooves 5 provided on the outer circumferential face of a spindle head are annular grooves in parallel with each other, they are communicated to each other through communicating grooves 8, and the connecting part of the communicating groove 8 is provided with a cutout of cylindrical projection. By passing cooling liquid from a cooling liquid feed device through the cooling grooves 5 being axial symmetry centering around the axis, because irregular thermal deformation is restrained to generate on the spindle head, fixing of bearings is attained, and the rotational accuracy can be improved. Further because the cutout is provided at the connecting part, rebounding is not generated between the two cooling liquid grooves 5 when the cooling liquid flows to the adjacent groove, and hence cooling can be efficiently performed.