Tool holder or spindle

A rotatable tool holder for driving a tool having a pitch against a workpiece, said tool holder being adapted to be mounted in a machine and rotated on a tool holder axis, comprising a driving cylinder, a driven cylinder reciprocatable and rotatable within said driving cylinder means resiliently connecting said driven cylinder on said driving cylinder, said driven cylinder being adapted to be attached with the tool, first thread means reciprocatable and rotatable together with said driven cylinder and having the same pitch as said tool, and a second thread means in threaded engagement with said first thread means and rotatable and reciprocatable relative to said driving cylinder, said second thread means having means engageable with a member angularly immovable about the axis of said tool holder for preventing rotation of said second thread means together with said first thread means and said driving and driven cylinders, such that rotation of said first thread means forces the tool to be advanced accurately with the same pitch of the tool, and further comprising means normally connecting said driving and driven cylinders for rotation together, said driving cylinder being disconnectable from said driven cylinder to stop said driven cylinder from rotating when said driven cylinder has moved to a predetermined position relative to said driving cylinder.