Abstract: A machine tool having a spindle assembly associated with an indexing tool storage rack on which a number of distinct tools are stored, and a transport or tool carriage for conveying a selected tool between the storage rack and the spindle assembly; and including a control circuit for sequencing the operation of the various component parts of the machine tool for either manual or automatic operation. The spindle assembly includes a variable speed motor drive for rotating a spindle having a drawbar for releasably securing a tool adaptor with the tool to the end of the spindle and which is associated with a push rod operable to control the release of the tool adaptor during a tool changing operation. A spindle gear shifting assembly is operatively connected to the spindle for shifting of the spindle between direct high speed drive and back gear low speed drive or to a neutral position in which the spindle is disengaged from the variable speed motor drive.