Great shot Geoff, you get about the same for acurracy as me , about 30secs and now and then 1 min unguided. Oh I always thought that black stuff was tar
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Another thing that helped with the tracking was that I diamond lapped the gears. Got some fine diamond paste, a power drill and some flexible hose to go from the drill to the worm shaft and gave both axis a 20 min go on a slow speed. Really smoothed out the tracking!! Well worth doing...
Make sure you clean the gears up well after before you regrease...
Cs Gary