Spindle end thrust adjustment is made by the threaded collar at the end of the spindle, just inboard of the gearwheel at the left hand end.
This is locked by a socket set screw (grub screw). Loosen this and tighten the collar to take up the play. There is a copper pad under the set screw to protect the spindle threads, so it may be tight.
If this doesn't do the trick then it's probably the thrust bearing at fault.
Edited By Robbo on 06/09/2015 19:45:55
Edited By Robbo on 06/09/2015 19:46:30