Gear hobbing machines

In a gear hobbing machine, the combination of a support, a rotatable hob, a slide mounting the hob for axial shifting on the support, a stepping motor operatively connected to the slide, a pulse source comprising a squaring circuit for deriving square pulses from the power supply and a frequency divider connected to the output of the squaring circuit, a relay energizable at the conclusion of a hobbing cycle and operative, when energized, to apply pulses from said frequency divider to the motor and thereby to cause the motor to impart a predetermined axial movement to the slide in response to each pulse, a subtractive counter for counting the pulses applied to the motor and a connection between the counter and the relay and operative to de-energize the relay, and thereby stop the motor, when the count in the counter is reduced to zero.