A hobbing accessory is disclosed for a vertical milling machine of a type comprising a column, a knee mounted to the column so as to be vertically positionable with respect to the column, a saddle mounted to the knee so as to be horizontally positionable with respect to the knee, toward and away from the column, a table mounted to the saddle so as to be horizontally positionable with respect to the saddle, in opposite directions across the column, a head projecting from the column, an arbor mounted operatively to the head and rotatable about a generally vertical axis, and a motor for rotating the arbor about the generally vertical axis. The hobbing accessory comprises a hob mountable to the arbor so as to be conjointly rotatable with the arbor about the generally vertical axis, an encoder mountable to the head for encoding rotational positions of the hob with respect to a fixed frame of reference, as the hob is rotated about the generally vertical axis, and for producing signals reflecting the encoded positions, a rotatable chuck, which is mountable to the table so as to be conjointly positionable with the table, for mounting a workpiece so as to permit the workpiece to be conjointly rotated with the chuck about a generally horizontal axis, a motor for rotating the chuck, and a controller responsive to signals produced by the encoder for controlling the motor for rotating the chuck.