PURPOSE: To stabilize operation and provide a self compensating effect by forming a fluid contact member into such a shape and a position as creating a force acting on a drive spindle member and by positioning it not to deviate from an appropriate position, before the drive spindle member taps a hole.

CONSTITUTION: After passing through a plurality of orifices 116, 118, 120 and touching an angle member 122, coolant pressurizes a drive spindle member 18 axially for generating a force in the direction for holding the drive spindle member 18 in an appropriate position. The coolant brought in contact with the angle member 122 flows in a chamber 124 under a pipe 44 and then flows in a conduit 126 for a tap. An exit orifice 128 formed in the drive spindle member 18 is connected to the outside of the pipe 44 and forms an exit passage to the circumference of the coolant infiltrated to the outside of the pipe 44 through a bush 112. On the other hand, a quick change mechanism 140 is arranged in the circumference of a tap support part in the drive spindle member 18. The tap is held in the drive spindle member 18 by a tap holding mechanism 142.