How to keep bearing expanders from popping out?

Hello,

The first time I removed the bearing caps on my South Bend 13x40, I screwed up and did not remove the bearing expander screws before removing the bearing caps. That was my fault as I never researched how to do it (I thought it was straight-forward.) and the plate, with the bearing adjusting instructions, was missing. I have since then replaced the plate, as well as repaired almost everything else on the machine as the machine was pretty much ready for the scrap yard when I got it.

Since then, it has become my "go-to" lathe and until last evening I was pretty happy with it. I had even quit calling it "my South Bend POS."

Last night, I noticed that the spindle climbed under load. So, I checked the clearance and found that it was about 0.005. Since I had to put in extra shims when I put it back together I figured that I probably just had to removed them and re-measure. I also checked to make sure that the bearing cap screws were still tight...and they were.

So, I removed the guards, removed the bearing expander plugs, removed the bearing expander screws, and removed the bearing cap screws on the bearing closest to the chuck. Then, I took a piece of bar stock and, by using the bearing cap screw holes, I rocked the bearing cap in order to remove it.

Once the cap was off, I found that the bearing expander was now on top of the bearing. (No, I didn't assemble it this way and there are no indents indicating that it ever was assembled this way.)

Well, to say that this really p*ssed me off is quite an understatement. This happened last night and I am still irritated this morning as I type this. To re-install the expander, by-the-book, I am supposed to pull the spindle, remove the bull gear, and re-install the expander. Then, I get to re-assemble everything. Well, I cheated as I did the last time. I found something that could be used to pry the bearing apart enough to squeeze that stupid expander back into place. Then, I filed any marks off of outside of the bearing and cleaned up the filings. Once assembled, and re-adjusted, I found that the spindle play is down to under 0.001. (Probably around 0.0005; but, my dial indicator goes down to 0.001.)

So, if I have to remove the bearing caps again, how do I prevent this from happening?

Thanks,

Brian

If I had mistreated the bearings and bearing expander such as this I would bite the bullet and replace the bearings and expanders. I suspect that you over tightened the expander to begin with. Tighten them with moderate hand pressure, maybe a couple of foot pounds, and install the screws that hold the bearing expander screws in place. You have likely "boogered" the bearings "V" surface from the inside so badly, that there is not enough surface to properly hold the expander V surface in place. Buy a couple of new expanders from Latheman2 of this BBS. He also has new bearings.

The removal of the spindle from the headstock is not a big deal. I can almost guarantee you that you have some brass down in the bearing area from the filing you did. Even a POS SB needs to have its spindle removed and the bearings and oilers inspected, after such abuse. I don't mean to be over critical.

However, you could make a .064" or so, brass shim (with screw hole openings) and glue it to the top of the bearing expander, to keep the expander from coming up. You would have to try the thickness of shims to see if .064" is too thick or too thin. Expanders are not hard to make--you could also made one with wider V.

Hello,

I did everything that I know of that I could to avoid the expander from coming out in the first place....and it still came out.

I agree with you that the way I re-installed the expander was not the best. However, in order to properly re-install that particular expander, I would have to remove the spindle and bull gear. At this time I don't have a puller for the bull gear and would have to make something up. Given all the other problems that I have had with this machine, I would put any money on it that the bull gear would not come off easily. In the end, I would probably have lost a minimum of several hours of time doing something that should have only taken 1/2 hour...even when I made every effort to ensure that everything was done correctly initially. This is why I want to know if I missed anything when I removed the bearing cap initially. Basically, is it my fault that this happened again? Is there something I should have done differently to prevent the expander from being pulled out of the groove? (Yes, yes, I know the re-installation was not by-the-book.)

The V groove, where the expanders go in is not damaged much...if at all, as I limited my "expanding" to the ends where the expanders do not contact the bearing.

Also, I think I got all of the filings out of the bearing; but..and I agree...there is no way to be sure without a complete disassembly.

Do to the expense, I am not buying new bearings for 2 reasons. The first is that plain bearings will work fine if there are only a few scratches. The second reason is that the fastest way for this thing to end up on parted out on e-bay would be for me to buy new bearings and have the expanders pull out again after taking every measure to ensure that the expanders do not pull out in the first place.

The bearings are made out of brass? I wonder what alloy. One thing I do like about South Bend lathes is that somebody once made a comment that a South Bend could be repaired by another lathe. Given the design, that is probably true. If I needed new bearings I have an 1893 Pratt & Whitney lathe that works great.

I like the idea about putting a shim above the expander. If this happens again, I'll see if there is enough space to do just that.

Regards,

Brian

jockofthelowveld said:

If I had mistreated the bearings and bearing expander such as this I would bite the bullet and replace the bearings and expanders. I suspect that you over tightened the expander to begin with. Tighten them with moderate hand pressure, maybe a couple of foot pounds, and install the screws that hold the bearing expander screws in place. You have likely "boogered" the bearings "V" surface from the inside so badly, that there is not enough surface to properly hold the expander V surface in place. Buy a couple of new expanders from Latheman2 of this BBS. He also has new bearings.

The removal of the spindle from the headstock is not a big deal. I can almost guarantee you that you have some brass down in the bearing area from the filing you did. Even a POS SB needs to have its spindle removed and the bearings and oilers inspected, after such abuse. I don't mean to be over critical.

However, you could make a .064" or so, brass shim (with screw hole openings) and glue it to the top of the bearing expander, to keep the expander from coming up. You would have to try the thickness of shims to see if .064" is too thick or too thin. Expanders are not hard to make--you could also made one with wider V.

Click to expand...

The bearings are made of bronze---660 bronze alloy, I suspect.

Something does not add up here...

Granted if you take the bearing caps off without removing the screws that pull up on the expanders, they can be pulled out as the bearing shells are free to expand and the expanders can slip out without damage to the shells.

How can such a thing happen if the bearing caps are held down against the bearings, keeping the split tight?

Are you sure you got the clearance right? You mention you added shims. Did you add too many and make it possible for the bearings (at the split) to separate in use?

Are the bearings damaged where the expanders are located? Is the space between the edges of the bearing splits wider than the expanders when the bearings are compressed against the spindle by hand with the top bearing caps off?

Were things damaged before you got the lathe by a previous owner?

It seems to me if the expanders somehow end up on top of the bearings when things are down tight then either the bearings are damaged, the expanders are damaged, or there are too many shims in place keeping the bearing caps from pushing down on the bearing shells enough...

Maybe other reasons as well...

Just some starting thoughs...