Abstract: An attachment for a vertical mill having a quill and a spindle rotatably mounted within the quill which is adapted to rotatably drive one end of a milling cutter. The attachment includes an elongated housing having a semi-cylindrical cavity and in which one end of the housing is clampingly secured to the quill of the vertical mill. In doing so, the milling cutter is contained at least partially within the cylindrical cavity. A rotatable center is rotatably mounted to the other end of the housing and the center is positioned within a conical recess at the lower or free end of the milling cutter or, alternatively, a pilot on the cutter is rotatably received in the other end of the housing. The housing together with the center thus allows the cutter to freely rotate with the spindle while simultaneously supporting the cutter against lateral deflection with respect to its axis of rotation.