Abstract: The attachment is to be fitted to a lathe or a milling machine. It is designed for slotting (keyway cutting) and grooving operations. It comprises an elongated boxshape housing having a longitudinally extending shaft journaled therein. The rear end of the shaft is operatively connected to an electric motor, while the front end carries a first bevel gear which meshes with a second bevel gear fixed to a hollow spindle and perpendicular thereto journaled in the front end of the housing. A rotary cutting tool is removably fixed within the spindle and projects laterally of the housing. The attachment can be detachably secured to the carriage of a lathe or to the head portion of a milling machine.