Abstract: A pneumatic drilling machine is provided, comprising a pneumatic motor, a circuit for connecting the motor to a source of compressed air, a tool holder spindle, and a drive mechanism. The drive mechanism comprises a coupling shaft which can be moved to select a first mode of driving the spindle and a second method of driving the spindle. The mechanism has a driving cycle which comprises a stationary mode at the beginning and end of the cycle, and at least one phase for driving the spindle according to the first driving method, then a phase for driving the spindle according to the second driving method, then the stopping of the supply of air to the motor. A supply valve of the circuit is controlled pneumatically by the drive mechanism to interrupt the supply of compressed air to the motor at the end of the driving cycle.

Abstract: A positive feed spindle with automatic retraction for driving a thread cutting tool is provided by using a fixed feed nut threaded on the spindle. A motor drives the spindle through a gear train that includes a first coupling gear with upper side teeth for engaging lower side teeth of a second coupling gear that also has upper side teeth engaging lower side teeth of a third coupling gear. The first and third coupling gears are continually driven by the motor in opposite directions through radial teeth of each. The second coupling gear on the same shaft as the first and third coupling gear is automatically raised when the spindle has been driven a predetermined extent by raising the shaft to disengage from the first and engage the third to reverse direction of the spindle. Radial teeth of the second coupling gear remain meshed with teeth of an idle gear in the drive train.

Abstract: A positive feed drill having a spindle drive gear train and a spindle feed gear train coupled to the drive gear train is provided with means for uncoupling the feed coupling gear from the drive coupling gear, and locking the feed coupling gear when the spindle has been fed a predetermined extent, thereby placing the drill in retract mode, and for unlocking the feed coupling gear, once the spindle is retracted, without recoupling it to the drive gear train, thereby placing the feed gear train in an idle mode until the aforesaid uncoupling means is manually reset. The drill is further provided with a rapid advance coupling gear keyed to drive a shaft which turns the drive coupling gear and with a rapid advance idle gear meshed with the rapid advance coupling gear. The gear ratio of the rapid advance coupling gear to the rapid advance idle gear is selected to be greater than the gear ratio of the feed coupling gear to the normal idle feed gear.