Hi Glen,
I realise that it is several years since you made this post. But I have a Mars Mercury lathe with exactly the same screw cutting table for gear set up. Did you ever establish what constituted a full set of screw cutting gears? Also note on my screw cutting plate that “driver” has had the “r” overstamped to read driven, and likewise driven has had the “n” overstamped to read driver. Looks like it was done at the factory. Driven is on top and driver is below as on your plate.

I am not completely sure which is which for the gears. Referring to photo no. 7 in your post, I believe the mandrill gear is the outer one on the shaft with the hexagon nut retainer. The driven gear and driver gear are both on the shaft immediately below with the knurled retainer. The large gear below that is an idler gear to transmit from the outer driver gear to the lead screw. Is this correct?

I have tried to set up for some threads, but don’t seem to have enough gears to fit a suitable idler. I have tried moving the y-shaped support and sliding gear shafts every which way, but can’t get a fit, hence suspecting that I am missing gears. Any help greatfully appreciated,

Regards,
Rob ( logon name robjean)