SB9 Rear bearing getting hot.
I have a 9x54 south bend lathe that i restored. it was sitting in storage since the 1950's. good overall shape. When i was getting the lathe restored and up and running I noticed the rear bearing was tight and was dragging the spindle turning by hand. I added .002 shim to it and it was running cool and did not have any problems.
So my spliced serpentine belt broke this weekend so I took it apart to install a solid belt, Lubed everything up and reinstalled everything and the rear bearing is now dragging again, So i put the dial indicator on it and added shims until i had .001 clearance(took .002 more). Now the spindle turns easy by hand but when running at 750 rpms it's getting hot quick. Humm. Im going to take it apart tonight and see what is going on.
Any tips or suggestions. I'm going to replace the felts and reshim for .0015 tonight and see what it does.
For oil I am using Motul 10w fork oil. Itís a full synthetic hydraulic oil used in motorcycle forks its has anti wear and anti foam additves but itís a hydraulic oil, Motul Factory Line Synthetic Fork Oil - Street Bike - Motorcycle Superstore
Why not go back to the same type belt you had before this problem?
It is, I had a spliced serpentine belt on it before, I just installed an unspliced serpentine belt and took the headstock apart to install it. Both are gates. Although the new belt's seem stretcher then the other one. The only thing I can think of is I tightened up caps tighter then I had them before and compressed the shims a little and it just needs more clearance for oil. The felts were not in the best shape so im going to go replace them and see how everything looks, Be back with an update in a min.
So the rear bearing was tight. It was a little shiny but no scoring, I only ran her 1min at the max. so I polished spindle and now i need to make some shims. It looks like i need about .001more than what I had. I also replaced the wicks will I was in there just for good measure as they were looking rough.
The down side is the lamented shim pack got damaged when I removed it so I'm going to haft to make them all new from the thick spacer up. And it's turning out to be tricky working with thin material. IT needs to be a good seal so it won't leak oil.
I'm guessing when I tightened the cap down I gave it more torque then before and it compressed the shim stack and it was on the edge of clearance anyway.
She is back togeather and running cool, It just needed a little more shim. Its got.0015 clearence. All is good in the world.
Now get the correct oil so it stays that way.
I'm going to order a gal of the Mobil stuff, although the fork oil is refined synthetic hydraulic oil with anti friction and anti wear additives it should be just as good if not better as spindle oil is just hydraulic oil. And I have gallons of the stuff as I own a motorcycle shop.
But what do you guys think should I drain it and get the right stuff now or do you think it will cause any damage.
I am using Mobil vactra #2 on the ways though.
I'm no expert on oils, but viscosity of the oil is the key factor that determines if it is suitable for the lathe spindle. Since the spindle has very little clearance (0.001") and rotates at high rpm, having a low viscosity lubricant is essential. Otherwise, using a higher viscosity lubricant would restrict the amount of lubrication delivered across the entire plain bearing, since the clearance is so small, and thus generate more heat, which makes the metal expand, limit the clearance even further, and finally lock the spindle. A positive feedback loop of sorts.
I'm thinking that sticking with recommended Mobile Velocite #10 for the spindle is a sound idea. But, compare the viscosity between "Motul 10W Fork Oil" that you are using, and "Mobil Velocite #10", and see if they are any where close. If that Fork Oil has a higher viscosity, best to flush it out with kerosene, and switch to Velocite #10.
But, I'm a noob, so maybe someone has a more experienced opinion out there.
Take a look at this chart: Viscosity Charts - Bob is the Oil Guy
10w should be about ISO 32. You could check the MSDS for the fork oil and see if it has more info.
I'm running Mobil 1 0w-20 synthetic in my head stock -- locally available and shouldn't sludge up.
Mobil 1 0W-20 Advanced Fuel Economy
Having pulled by headstock apart, and cleaned out 40+ years of sludge, I'm convinced that synthetic oils are the way to go.
Google tuned up a better chart. Mobil Velocite 10 is an ISO 22.
Good info! Thanks guys, It looks like the Motul 10w has a Kinematic viscosity @40*c of 35.9 which puts it right at a iso32, The 5 weight had a viscosity of 17.9. So a 50/50 blend of 5w and 10w should give me an iso 22. Motul stays its fine to blend the oils and even sent me a chart with the ratio for different weights by blending.
I have a ton of the Motul left over from the shop and just found 7 more quarts of the 5 weight so I'm going to blend it until I get around to getting the Mobil stuff. Does Mobil make a synthetic spindle oil?
The lathe seems to be running better than ever, although its weeping a little oil from the rear shim pack, I need to do the trust bearing upgrade as the fiber washer does not seem to be sealing well. The front bearing uses a drop ever couple hours or so at the most.