For all machine screw jacks a keyed lifting screw is available. Note the keyway in the screw causes greater than normal wear on the internal threads of the worm gear.

For ball screw jacks the lifting screw cannot be keyed, as the keyway would interrupt the ball track, permitting loss of the recirculating balls. Instead the option of a square anti-rotation tube can be fitted to ball screw jacks to prevent rotation (refer to E-Series Screw Jacks brochure (P47) For further details consult Power Jacks Ltd.