Axial slip of the lead screw is a common cause of thread inaccuracies. A slight oscillation imparted to the screw will cause a periodic error in pitch. Georg Schlesinger adopted a pass-off criteria of half of one ten thousandth of an inch of slip for the 1920's German machine tool industry. To adjust clearance in the right hand bearing of the Myford Series 7 lead screw is a difficult balancing act, generally resulting in excessive thrust loads.
This modification, carried out on the right hand bearing, provides two precision needle thrust races to accept the load when screw-cutting. The hand wheel also becomes more certain in its action.
Instructions and drawing plus needle races, ground and hardened thrust washers, free cutting steel and bronze to replace the existing bushes are all included. This kit suits all Super 7 and ML7 lathes fitted with either a Ø5/8" or Ø3/4" leadscrew. No modification is required to the leadscrew. A very worthwhile project.