Abstract: A machine tool mount which can concurrently serve for centering or positioning the spindle of a machine tool. Within a socket holding a shaft to be fitted to the spindle is an externally rotatable eccentric shaft, a movable piece contacting said eccentric shaft, a pressing piece contacting a spherical surface of said movable piece and a sphere contacting said pressing piece. The front of said sphere is held in the socket by means of a semispherical cover having a central hole through which projects a centering needle. The centering needle is removably attached to the front of the sphere.