)My lathe is a WWII (1944) South Bend "Heavy 10" that I acquired nearly 40 years ago. It had done 20 or more years in a community college and finished its days turning commutators for generators and starters so it was beat alltohell but was all I could afford. It had a 4" Cushman 3 jaw chuck that was beyond worn out! The bed had a drop of 0.0015" near the chuck and the best I could get the run-out on the chuck was 0.020" even after dressing the jaws. It was not a big deal since the only lathe work I had done in the past was 'crude' (though it did build a 1/2 scale traction engine in 1995/96).
Since I plan to do some work on my 7.5" gauge American this winter, I needed better accuracy so decided to see what I could do with the old South Bend so I stated by putting a dial indicator on the spindle. The dial indicator measures to 0.001" but there was no noticeable (let alone measurable) run-out on the spindle! I couldn't believe a 73 year old lathe could be that good so I checked and re-checked my setup but it was correct!
I considered making a 5C collet holder to fit the sleeve in the headstock but decided a 3 jaw chuck would be the most handy and versatile so last week I purchased a 6" Shars 3 jaw self-centring chuck with the backing plate for the South Bend 2-1/4 x 8 headstock.
This morning I turned the backing plate on the South Bend with as much care as I could manage and got a good snug fit to the chuck with less than 0.001" run-out on the chuck body. I don't have any drill rod but I chucked a piece of cold rolled steel and measured the run-out - less than 0.003" without any 'fudging' or fiddling!
That's quite an improvement over 0.020" ! I left the shop with a BIG GRIN on my face and feeling really good about my old South Send! IF I need better than 0.003" I am sure it is possible now!
(Just HAD to share!)