Delta Milwaukee 12" Lathe Renovation Project Questions regarding bearings

[Mark R Webster]

I am renovating a 1946 Delta Milwaukee 12” Wood Lathe. It has been outside, under a roof for nearly 30 years, the last 5 yrs outside covered with plastic but in marine air. There is a fairly light to medium coat of rust pretty much everywhere. I plan to disassemble the lathe as much as possible, remove any rust and clean up all surfaces to put it back in working order. The spindle seems to turn freely and I can’t manually feel any looseness or play. I don’t know if the bearings have dried out and could run more freely if I replaced them. Looking at the original manual, it says:
“The bearings on the headstock are preloaded at assembly by shimming behind the outboard bearing in order to insure a rigid yet free-running spindle. IT IS VERY IMPORTANT, THEREFORE when removing the spindle and pulley not to disturb the outboard bearing.”
If I decide to replace the outboard bearing how would I do that with out adversely affecting the preloading and shimming. Should I expect the bearing were sealed and would have not been affected by moist air over the years. How freely should the spindle spin? Suggestions…. Thoughts?
Thanks
Mark

[Mark Wooden]

Unless the bearings were replaced just before it was put outside, you'll need to replace them; doubt there will be any viable grease in them. As far as replacing them, info on a headstock rebuild and preloading the bearings can be found over at OWWM.org

[Mark R Webster]

Thanks Mark, I spent some time looking for information on OWWM.org regarding this a while back, but was only able to find the original manual. As best I can tell it doesn't discuss this. Any hints on finding the information specifically regarding the headstock rebuild?

[Benjamin Miller]

If the outboard bearing has shims behind it, a good starting point for preload would be to reuse those shims and see what you get.

Spindle bearings in machine tools are usually preloaded such that the spindle rises to a warm, but not hot, temperature after a period of running, say a half hour. In the absence of a specific temperature in the manual, 120 degrees F would be a good starting point. I would use a cheap non-contact digital thermometer to check the spindle temperature, and if the spindle is not hot enough, add precision shim stock or tighten a preload nut if you have one.

The end goal of preload is no play when the maximum force is applied, so if you could figure out how much force you will apply, you could also use a dial test indicator to check for play. I would bet that chucking up a maximally sized piece of wood will apply as much thrust as this bearing will ever see.

[Benjamin Miller]

The manual shows that your lathe uses ND 88505 bearings, and of course, New Departure hasn't been around for decades.

You're fortunate in this case, however -- 88505 bearings seem to be a fairly standard part, and are often available as wheel bearings. You can find them on ebay for less than $20 each, and Advance Auto has them for about $25.

Note that 88505 bearings are almost, but not quite, the same size as common 6205 bearings. 6205 bearings are a tiny amount narrower, so that would definitely affect your preload. If you had a surface grinder and lathe lying around, you might be able to make a wider shim and convert to much cheaper 6205 bearings, but I suspect you'll be stuck spending the $50.

[Mark R Webster]

Thanks for the info and suggestions Ben. I will check out the bearings.
Mark

[Mark Wooden]

Accurate Bearing- http://www.accuratebearing.com- is sort of a 'go to' bearing house for replacements in older machinery and they have lots of experience in supplying them for Delta lathes.
Bearing pre- load has been discussed over on OWWM many times, you need to search the main forum.

[Mark R Webster]

Thanks Mark

[Mark R Webster]

I pulled the bearings off the lathe and discovered that they are labeled as New Departure C88505. Is the C88505 different in anyway from an 88505? It looks like the original shims are gone but were replace by what appears to be a single home made shim. The shim was pressing on the outboard side of the bearing rather than againts the pully side of the bearing as shown in the parts diagram of the original manual. Is the side the shim is placed important as long as the thickness is correct?

[Benjamin Miller]

Any 88505 bearings should work. A wood lathe isn't a super critical application, so I would get some cheap ones from an auto parts store. They'll probably give you ones with rubber seals, instead of the metal and felt ones you have.

The shim definitely needs to be on the inside of the spindle, toward the pulley. The retaining nut on the left side of the diagram secures the inner race of the bearing to the spindle, but the inner and outer races can still wiggle back and forth a bit. The purpose of the preload shim is to push the outer race away from the other bearing, thus removing the slack from both bearings by stretching them a bit.

McMaster-Carr carries shims and shim stock. If they don't have a shim in the size you need, you could buy some .003" shim stock and make your own. .003" steel is very thin, so you might be able to punch it with a hardwood dowel and block with a hole. If you can't, a gasket punch would work for the inner hole, and scissors can cut the outer dimensions.

[Mark R Webster]

Thanks Ben I will check with my local auto parts store. Just curious, what is the difference between the C88505 and the 88505 are they the same dimensions ie thickness... is it the seal type? Sorry for my ignorance but, what is a non contact thermometer, and how does one check the spindle temp with one? I know wood but very little about metal/machine work .

[John Downey]

How do the old bearings look? Didn't sound to me like you needed new ones - spins freely with little run out? Does the lathe headstock have an oil cup?

[Mark R Webster]

No no oil cup, not sure how well they spin, seems they could spin more freely.

[Benjamin Miller]

Yeah, the bearings you have should have metal shields with felt seals on the inside. The grease inside them is well past its expected life, so you should replace them.

I generally replace sealed or shielded bearings in machinery whenever I have it apart, because they usually don't cost much. Really high precision bearings tend to be open and oil lubricated, so you can run them through a cleaning bath and reuse them. The bearings in my milling machine, for instance, cost over $1000 to buy new, so I make sure they stay well lubricated.

[Mark R Webster]

Thanks Ben, Sorry for my ignorance but, what is a non contact thermometer, and how does one check the spindle temp with one? I know wood but very little about metal/machine work