PURPOSE: To make it possible to align the center of a hole to be machine with the rotating center of a quill at the position of insertion of the quill, by providing a mechanism for conveying a workpiece to the position of insertion of the quill, and a locating pin adapted to be fitted into a locating hole in the workpiece.

CONSTITUTION: A conveying beam 5 is driven in such a condition that the beam 5 is raised while an engaging pin 8 is inserted into an engaging hole 9, and therefore, a workpiece 1 is conveyed to a quill inserting position on a base 13 along a conveying guide rail 4. After a quill delivering and receiving means inserting a quill 11 in a hole 3 to be machined in the workpiece 1, the conveying beam 5 is lowered to release the engaging pin 8 from the engaging hole 9, and a locating pin 14 is raised to fit its front end part into a locating hole 15. When the locating pin 14 is fitted in the locating hole 15, the workpiece 1 is guided along a tapered surface 16 on the locating pin 14 to be laterally moved, thereby it is possible to hold the workpiece.