This invention relates to the art of automatic fastening machines, and more particularly to a new and improved drill spindle drive for such machines.

One area of use of the present invention is in automatic drilling and riveting machines, although the principles of the present invention can be variously applied to other automatic fastening machines. In drilling holes in certain metals for insertion of rivets or other fasteners, it is necessary to drive the drill at low speed and with high torque. Electric motors have a number of advantages in terms of lower energy requirements, fewer maintenance problems and quieter operation. Therefore it would be highly desirable to provide a new and improved drill spindle drive for automatic fastening machines employing an electric drive motor and having low speed controllability and high torque.