Hi Mike
The thrust bearing on mine was located between the main bearings against the right side of the left spindle bearing. The thrust bearing itself was a large ball thrust bearing from memory about 20mm thick. the main bearings were bronze bushes. you have to keep them well oiled or they will seize.
To remove any play the thrust bearing is tightened against the spindle by a large threaded ring at the left hand end of the spindle that also retained the drive train gear and a collar. you will need a pin spanner. you should find the bearing under the small cover to the left as seen in your photo.
The back gear on mine was under the spindle within the headstock.
It was made from cast Iron as was the bull gear. The gears were badly damaged when I got the lathe. I had to repair teeth on the large back gear and replace the small pinion altogether. I also had to make up a new bull gear from one scrounged from a dealer not easy to find. It was a big job.
If yours are intact without missing teeth you are lucky. Clearly they do not like to be overloaded.
You will probably find there is only a single half nut that engages the leadscrew for screw cutting this is moved down onto the leadscrew by a lever. It too is cast Iron, it is guided by a 3/4 inch (from memory) cast iron spigot. I managed to break that one day while cutting a heavy thread. The fix for that was to bore a slightly smaller hole in the nut body and Loctite in a stepped 3/4 inch mild steel pin to replace the cast iron pin… I still have the pin! saw it the other day in a box….
For Colchester not a good design. It was bound to break one day. Mild steel is better.
The gears on the back of the apron are open. there is no sealed gearbox I would dismantle the apron and clear out the detritus that has accumulated there before greasing everything and reassembling.
One nice feature of the lathe is how easy it is to adjust the headstock alignment. Just loosen (firm not too loose) the 4 bolts that clamp it down (Look up under the headstock between the ways) You can then adjust the spindle axis until it is perfectly parallel to the bed via small jack screws under each end of the headstock.
Regards
john
Edited By John McNamara on 13/09/2015 14:32:10