Went down this morning to do a little grinding, using the MicroMark tool post grinder for the 7 X 12 lathes. Couldn't hold the size, and noticed that when I reversed the feed, after grinding to the shoulder, I got a spark. Only logical answer is play in the carriage,I hadn't touched the cross slide. Time to take it apart and find out what's going on.
After removing the apron, and the gibs, blued up the V in the carriage and moved it over the bed, not an even pattern, but the heavy parts were at the ends, which is where I'd want them to be. An indicator had shown some .002" movement when I tried to twist the carriage on the bed.
Didn't particularly like the wear pattern on the lower gibs, so they were pulled and ground flat then deburred. Cleaned everything off and gave them a shot of oil, then put the gibs back on and tightened to give a nice sliding feel. This time, when I tried to twist the carriage, nothing showed on the indicator. Ok, end of that problem, but as long as the apron is off, let's look at the carriage handwheel and the slop in the fit there. Found the shaft is .015 over 3/8", and the bore it ran in is .004" over that. Turned and polished the shaft to .375", then bored the apron for a bronze bushing. Pressed it in, reassembled, and the thing operates much smoother than it had before.
My thoughts are that the gibs being not flat, a proper adjustment, no play, but no binding, was not possible, and flattening them elimnated that possibility. One was just curved, the other had several waves, but taking .002" off each one, back first then the working surface, eliminated the problem there. The front one felt rough when I put it back on, pulled it off again, stoned all the edges, end of that.
Next victim is the tailstock, trying to get that last few tenths taper out by tapping here or there on it because there are no screws for the setover is a pain in the butt, but there also isn't a lot of metal there to work with. Also thinking of some way to add another stage of gearing to get the feeds down lower. .005" may be low enough for larger work, but I'd like to see less than half of that for some of the tiny stuff I do. Lennie the Lurker