Looking for sealed tapered roller bearings

[Ischgl99]

I thought about adding some zerks to lube the bearings as well. But, not being sure just how grease could be directed into the rollers and thinking that excess grease would get all over the interior of the headstock, I gave it a pass.

You don’t want to inject the grease directly into the rollers, grease gets injected into the housing around the bearing and acts as a reservoir where the oil in the grease is drawn into the bearing over time. Any grease that is in the bearing gets pushed out as soon as it starts spinning, so making sure the void around the bearing has grease provides the lubricant the bearing needs. The bearings themselves require very little grease to be properly lubricated, just think of how long a sealed bearing lasts with just the amount of grease inside the bearing. The only exception to this is double row bearings, or back to back arrangements, that have the grease injected between the two rows of rolling elements and eject the grease outward, instead of the grease coming from the housing and going into the bearing.

To keep the headstock clean, and there is room, you could install an inner bearing cover on the headstock side and inject grease in that side so it gets pushed out the spindle end. You could add an opening towards the bottom that ejects the grease downwards. This of course is making it much more complicated, but who doesn’t need another project??

 

[homebrewed]

You don’t want to inject the grease directly into the rollers, grease gets injected into the housing around the bearing and acts as a reservoir where the oil in the grease is drawn into the bearing over time. Any grease that is in the bearing gets pushed out as soon as it starts spinning, so making sure the void around the bearing has grease provides the lubricant the bearing needs. The bearings themselves require very little grease to be properly lubricated, just think of how long a sealed bearing lasts with just the amount of grease inside the bearing. The only exception to this is double row bearings, or back to back arrangements, that have the grease injected between the two rows of rolling elements and eject the grease outward, instead of the grease coming from the housing and going into the bearing.

To keep the headstock clean, and there is room, you could install an inner bearing cover on the headstock side and inject grease in that side so it gets pushed out the spindle end. You could add an opening towards the bottom that ejects the grease downwards. This of course is making it much more complicated, but who doesn’t need another project??

The interior of the headstock casting is the original sand-cast surface so bearing covers in there, if they could somehow be installed, wouldn't seal. I don't know how one could machine those surfaces, much less drill/tap mounting holes for the covers. The bearings are 32mm ID and 60mm OD, and seat in pockets whose bottoms have a 55mm bore to accommodate the spindle. So no 90 degree access to anything in there.

The headstock is a little under 4.5 inches wide and there are 4 transmission gears in there to select between high and low RPMs, plus a couple of spacers on either side to keep the gears lined up properly. Not a lot of room to do much.

 

[Ischgl99]

The interior of the headstock casting is the original sand-cast surface so bearing covers in there, if they could somehow be installed, wouldn't seal. I don't know how one could machine those surfaces, much less drill/tap mounting holes for the covers. The bearings are 32mm ID and 60mm OD, and seat in pockets whose bottoms have a 55mm bore to accommodate the spindle. So no 90 degree access to anything in there.

The headstock is a little under 4.5 inches wide and there are 4 transmission gears in there to select between high and low RPMs, plus a couple of spacers on either side to keep the gears lined up properly. Not a lot of room to do much.

Sounds like nothing of concern in there if some grease from the bearing gets inside. If you are greasing it properly, very little would make it into the headstock over the life of the machine anyways.

 

[Jake M]

Sorry I can't be a lot of help on the bearing selection, except to say that IF (and yeah, that's a big if.... The dollars and cents thing in that department is real....), but IF you went with angular contact bearings, they are way more rigid than the internet as a whole gives them credit for, and a shielded pair (not sealed, sealed wants to go slow), but shielded angular contacts would outlast that lathe with the lubricant that's pre-installed. A simple felt (or goop) gasket and wiper on the covers would keep the big chunks out. They really are good, but cheap is not in their vocabulary.

Snip.......

At the moment there is no way other then to per-lube the bearing with Molly-grease before installation.

There's a lot of people all over the internet who swear that molly grease is the most amazing thing ever, and they might be right. But I wouldn't recommend it in this application. It's far better for "rough" things. Sintered metal parts, rusty old dump truck trunnion pins, and SLOW moving bearings, bushings, and such. Automotive CV joints love it (although it's a lower weight than you want). Heavy truck universal joints in the driveshaft love it. Tapered roller bearings, not so much... Grease isn't a good/better/best thing, it's an application thing. The "magic" that is in molly grease (molybdenum disulfide) is a solid lubricant. Great for filling voids on uneven, imperfect surfaces, but you don't want to lift roller bearings off of their races. If I recall, I think This Old Tony even half heartedly disclaimed that molly grease was all he had at the moment or something to that effect.

I'd suggest a lithium complex NLGI number two grease with a CG rating (preferably without the LB rating, but that's splitting hairs, CG-LB would do fine). You don't want EP, as you won't stress it enough to wake that feature up from it's nap, let alone put it to work. Save that space for more oil... Unless you figure out how to seal them. If you figure that out, a simple, hardly modified, R&O ammended circulating oil in there would be ideal. You wouldn't ever need to turn the lathe off, you could leave it run twenty four hours a day, seven days a week, and when those bearings wear out, your great, great grand kids will be too old to care if it ever gets fixed.

Really, oil is the ideal solution, but for practical reasons (just like wheel bearings in cars with that type), the best answer is to use a grease which will most closely emulate that. Your bearings will run cooler (set up properly, apples to apples of course), and rob less horsepower from your lathe.

Yeah, I know..... Oil discussions and the internet..... Bottom line truth of the matter- I have never run one of the lathes like or similar to what you have, but I was given a "take out" set of bearings, just for "science". I ended up using them to make a hand cranked hose reel. I can tell you this, regardless of what lube or lube mechanism you choose, even if it's inadequate in it's type and it's quantity... If you bought an off the shelf bearing from a name brand, IDENTICAL dimensions, type, style, and options to what you took out, you'd be light years ahead. Whatever parts and methods you decide on, I think you'll be happy with it.

 

[Stan the Man]

STRB is a spherical thrust roller bearing, that is a different design than a tapered roller bearing.

You are correct Sir! STRB does stand for Spherical thrust roller bearing however in my own defense I used that abbreviation in my written piece so I didn’t have to keep writing Sealed Tapered Roller Bearing over and over. Having said that lesson learned. I will be sure not to do that again. Thanks for your addition to the conversation.

 

[Stan the Man]

I thought about adding some zerks to lube the bearings as well. But, not being sure just how grease could be directed into the rollers and thinking that excess grease would get all over the interior of the headstock, I gave it a pass.

I also realized that if the spindle is polished down so the rear bearing is a light friction fit, you have a setup that can actually be taken apart to lube the bearings....without risking damage to them. Once the retainer nuts are removed, the rear inner bearing and the transmission gear are the only things keeping the spindle in the headstock. And the transmission gear is a sliding fit as well. Not to say it won't be a PITA but I think it could be done without removing the headstock from the bed.

It also might be possible to loosen up or remove the bearing covers and get grease into the bearings that way. The rear cover can be completely removed so no access problem there. The front one would be a little more challenging since it can't be completely removed. I thought about using oil on the bearings instead of grease, just to make it easier to lube them; but all of the descriptions I found regarding bearing replacement used grease. So I did too.

Homebrewed, thanks for your input to this discussion, I have a much better understanding of bearings and lub and such for this project now thanks to all the guy's that joined in. Your idea of removing the bearing cover and painting the cone end of the bearing say once a year then buttoning it back up isn't all that unreasonable and will help me get the head back together. Couple 3 questions for you. When you polished the spindle down for a light friction fit what product did you use? Emery paper and what grit , scotch bright pad what color or other product? What did you have the most success with? Question 2 when you machined the inside surface that faces the bearing did you just take a few light surfacing cuts across the whole face, then test fit the cover till it was flush with the outside housing cover? Last question, do you see any advantage to machining a set of aluminum covers to replace the plastic ones?

 

[Stan the Man]

I was referring to the spacers which fit on the side of the spindle away from the chuck. They are keyed and fit between the back of the spindle where gear mesh occurs. The thicker bearings require the spacer be thinner so that gears maintain 100 percent mesh and alignment. I am including a picture of two I made, with keyway, for this purpose. The second picture is where the spacer fits.

Thanks for your input to this discussion, I'm learning a lot talking to every one. Also thanks for the photos makes it easier to understand what your talking about. The spacers you are showing and where they go are not very thick the spacer on my grizzle without measuring in the same location is about 50-62mm in length the ones your holding look to be about 6-8 in thickness. Just curious about your set up and which machine you have.

 

[Larry$]

Just a thought about spindle bearings based on machines that I have serviced. Wood molders, made in Germany. Spindle speeds 6 to 8,000rpm. Tooling: up to 9" long solid steel 5"+ in diameter unsupported on outer end. Heavier tooling is carried on out board bearings. Tooling end of the shaft has two angular contact ball bearings that come as matched sets and are installed so the pre-load stack of spring washers force them against their deep groove sides. Very heavy spring washers. The other end is supported by a single ball bearing that has a sliding fit to the housing allowing all heat induced movement to move that end and not the tooling end. All bearings on the lower cost machines ($100K) are lightly greased when installed and have no means of adding grease. The bearings are protected from dirt by metal labyrinth caps. No rubber seals. High speeds, large diameters and rubber generally don't play well. These are well balanced systems and will run for many thousands of hours before needing bearing replacement. Fairly expensive bearings! It takes some special tools and a 20 ton press to service them. High production machines use oil mist lubrication systems.

I'm currently waiting for motor spindle bearings to come from Italy for a 20,000rpm spindle motor on an automatic edgebander. Luckily we keep a spare set of motors on hand. Odd bearings and they are on back order!

 

[homebrewed]

Couple 3 questions for you. When you polished the spindle down for a light friction fit what product did you use? Emery paper and what grit , scotch bright pad what color or other product? What did you have the most success with? Question 2 when you machined the inside surface that faces the bearing did you just take a few light surfacing cuts across the whole face, then test fit the cover till it was flush with the outside housing cover? Last question, do you see any advantage to machining a set of aluminum covers to replace the plastic ones?

I used 200 grit wet/dry. Before doing it I covered the entire mill table with a clean shop cloth to keep grit out of the machine workings. It took less time than I had anticipated so if you do this start testing the fit pretty early on. You could use one of the old bearings for this, no need to risk getting grit into one of your nice new ones.

I did NOT modify the headstock in any way---at least, not for replacing the bearings*. I modified the bearing covers, basically machined a groove on the inside to provide enough clearance for the added protrusion of the bearings. All the stick-out is on the outside so the spacers on the inside (on either side of the transmission gears) didn't need to be messed with.

If you have a large enough machine, there's nothing wrong with machining your own bearing covers out of aluminum. I think it might be possible to make a 2-piece cover for the front bearing -- they would overlap in a half-lap fashion -- which would make it possible to completely remove the bearing cover. That would make it easier to stuff more grease in there when needed. Now I'm wondering if the inside portion of the covers could be machined to provide a grease reservoir for the bearings. Hmm.....

*I drilled a hole in the headstock where the speed controller mounts so I could spray lithium grease on the transmission gears. When installed, the speed controller box covers the hole so it's a mod with almost no effort required.

 

[Stan the Man]

Hi Hb.
Thanks for your reply, looking back at what I posted I should have said Wet Dry rather then emery , I will do that use the wet dry. I agree covering the bed of what ever machine you grind on is important to keeping things from going south with grit. I have another larger lathe I can use to make the modified pieces for the 7 x 12. I think I will use the plastic cover as a working model then machine two aluminum plates to replace the plastic.

Its funny you mentioned a two piece cover as I was also thinking along those lines. However I want to explore your idea of creating a well or reservoir for grease. There would be more then enough room to access the back side of the bearing cover behind the mounting plate of the chuck, then its just a matter of smearing grease into the reservoir and putting it back into position. Great Idea !!!

I saw a guy add two threaded holes to the top of the case, one directly over each gear1/4 -3/8th dia. big enough to visually inspect the gears as well as add lube via gravity then made two brass plugs to close them up. Another fellow added a larger plate over the top of the case with a padded surface to lay tooling on. Perhaps a combination of both ideas would allow inspection/lube when needed and a larger surface to lay your chuck wrench or other items as found on larger machines. So many options. LOL.

What mods have you done so far and which ones would you still like to do?
Stan.