Abstract: A tractor drive for feeding continuous paper in an office machine has a drive shaft provided with an axially extending groove; a tractor housing; a drive wheel rotatably supported in the tractor housing; a transport member connected to the drive wheel to be driven thereby and arranged to project into marginal perforations of the paper for transmitting a feeding force thereto; a bearing sleeve affixed to the drive wheel and coaxially mounted on the drive shaft; a feather key carried by the bearing sleeve; and an actuating member operatively connected to the feather key. The actuating member has a clamping position in which it presses the feather key into a clamping contact with the bottom of the drive shaft groove, whereby the tractor (formed of the tractor housing, the drive wheel, the transport member and the bearing sleeve) is axially immobilized relative to the drive shaft.