1929 South Bend 9A Question

A little background: I purchased this south bend from an older fellow. He is friends with my father who told me he had a lathe. I showed interest in it and he sold it to me for $1100. Some of the gears had missing teeth but I have replaced them and I also had to replace the motor so I think the price was fair being that I knew I still had to spend more money on it.

To the meat and potatoes: If I chuck up a long piece of metal stock in it, at the very end of that stock work you will notice a slight wobble as it is rotating which ultimately means it isn't running true... obviously. I replaced the 6" atlas 3 jaw chuck with a brand new 7" south bend 3 jaw chuck that cost me a little over $700. After that the wobble became far less dramatic but was without a doubt still there (so this was still a good buy I figured because the chuck needed work done to it replacing anyway). After reading through posts on this website, I became aware that it may be my brass bushings on the headstock causing the wobble, and have come to the conclusion thats exactly what it is. After taking the headstock apart, the first thing I noticed were shims in between the two halves of the bushings that clamp the spindle in place. I read that wear on these 1920-1930 model bushings are a common problem that cause the work to stop running true. If I grip the work stock and lift up you can definitely feel the play in the bushings closest to the chuck. This was confirmation for me that the wear on the bushings was to blame. However, I never could notice it on the other side, but I am sure it is there as well. Ever since I decided that this was the problem a year ago, I have since purchased from of eBay 2 different headstock castings (making a total of 3 castings and 7 pairs of bushings), one of which was an entire headstock assembly (just to ensure I had enough parts) and two spindles (well only purchased 1 spindle but ir is now a total of 2 that I have), all which were very hard to come by. I'm experimenting with the second headstock casting right now. It has play in it as well. The last one has an extra pair of bushings and seems to be in better shape than the first two. I am hoping I will get lucky and one of the pairs not have so much wear but I am not very optimistic. Aside from making brand new bushings, what in the world can I possibly do to fix this "wobble"? I just do not see how shims can be the answer. Wouldn't shims cause more of a gap, and more play? Any and all suggestions/advice for me would be much appreciated.

If you've been willing to stick all that into it, I would surely look into having someone make you some bronze bushings if you can't yourself. Honestly the casting itself isn't the issue. It's either the spindle, bushings/bearings, or both. Pick the best spindle and have some bushings made.

1. those bearings look fine. put it back together, set the clearance correctly by removing shims, and use it.

2. long pieces of stock ALWAYS runout at the end. That's why the lathe has a tailstock with a center.

3. the lathe is not a 9A, that is a term which is generally used to describe the later, lighter, 'workshop' models.

allan

Just from reading the op first post I believe kitno nailed it. How far is this thing hanging out of the chuck? The bearings are useable. Bolt them back together without the spindle and run a brake cylinder hone through them. They do not have to be honed to a completely new surface. If there are no shims in them run the top bearing over sandpaper on a flat surface. Take a few thou off. Very few. Polish up the spindle. Bolt the spindle back in and either shim to get clearance or sand more off. Can't take more than an hour of time to have that spindle running like new. Measure the up and down at the spindle threads end. 1-2 thousands is OK. You need room for oil. Run the spindle for a period of time to see if it heats up. No heat, Great. If getting warm maybe a .0005 shim or so. You would have to do the same thing with brand new bearings if you have them made or if NOS was even available. Those bearings from the factory were scraped into perfect alignment. They just need a little TLC. If you can get a morse taper test bar that would fit your spindle that is the way to go. After reassembly you can check whether your spindle is running true with the bed--side ways--up and down and parallel. Changing the headstock and using other bearings is opening a can of worms. Good luck.

If you're using a 3-jaw chuck, more than likely that's what's causing the runout, even if it's brand new. Pretty much normal for a 3-jaw.

Uh, I strongly suggest you NOT run any kind of hone on the bearings, or polish the spindle. The bearings are sort of lemon-shaped in cross section, with clearance areas for felt at the split line. Not the kind of thing a hone is supposed to be used in.

Also, whatever precision the spindle has comes from concentricity between the bearing surfaces and the taper and shoulder. Those features were ground in situ after the bearings were finished. If there are adhered lumps of material on the spindle's bearing surfaces, remove them with a soft scraper, but don't otherwise modify the spindle.

allan