How Should These Spindle Bearings Be Lubricated? Also, What Bearings to Buy?

[ChandlerJPerry]

I honestly don't know what the radial bearing is doing, so I'm not sure if it would make a difference or not.

I used to work in the bearing industry, they estimate 10% of the bearings sold worldwide are counterfeit, so I avoid buying bearings on Ebay or other non-authorized distributors. The first bearing you show is selling for 10% of the normal price, that is a huge red flag for me. You can go to this website and scan the bar code of the bearing box of the second listing and it will let you know what that bar code belongs to and if it matches what is on the bearing. https://www.stopfakebearings.com/ Look and see if there is high spot markings on the bearings, I know NSK does that on their precision bearings, so if that is missing, then it should be a hard pass. You might not be able to see it in the pictures, maybe you could get the sell to get you better pictures.

Thank you for the insight. The QR code on the box isn't quite scannable so I have requested a better image of it from them, as well as pictures showing any high spot markings.

Concerning the price on the first bearing, I would normally be inclined to agree, but the seller appears to be a reputable industrial surplus dealer. The first picture of the listing shows a very weathered looking box and an inspection certificate bearing a 1990 date. It's also the only one they are selling unlike many dubious operations on eBay that sell these things en masse at suspiciously low cost. Could it be a counterfeit? I guess anything is possible, but it would be a lot of work to make all this up to sell one bearing for $40. It could have been a counterfeit back then too I suppose.



I'm a little more dubious of the NSK bearings considering that they are in new appearing packaging. Definitely would like to scan the QR and scrutinize them more closely. The seller only has two available and has been on eBay since 2001 with positive feedback, but that doesn't mean that they aren't unknowingly selling a fake.

 

[Ischgl99]

Yes, there could be reputable sellers selling counterfeits that they believe are real. Many of these bearings come from businesses that are getting rid of old stock, and who knows where they got them from. Most likely an authorized distributor in the case of larger businesses, but it's still a gamble. There is a company I worked with that built their business buying overstock from companies emptying out their storerooms. At so many plants, the maintenance personnel buy extra to have on the shelf, then when it comes time to use them, say they are old, I'll get some new ones, and a couple extra for the shelf, and the cycle repeats until someone buys all their old stock LOL.
The older NTN bearings are most likely authentic, I don't think I have seen any cases of the counterfeiters using anything other than new looking bearings. Is that a sealed bearing, I can't tell from the picture if that is a seal of the cage. The part number does not indicate seals, so I am guessing that is the cage. The preservative is old and dried out, so you will want to clean it out good with a solvent before using if you choose to buy it. If that is sealed, then the grease would be bad sitting for that long and would need to be cleaned out before using. That one looks like it would be worth the risk.

 

[ChandlerJPerry]

The older NTN bearings are most likely authentic, I don't think I have seen any cases of the counterfeiters using anything other than new looking bearings. Is that a sealed bearing, I can't tell from the picture if that is a seal of the cage. The part number does not indicate seals, so I am guessing that is the cage. The preservative is old and dried out, so you will want to clean it out good with a solvent before using if you choose to buy it. If that is sealed, then the grease would be bad sitting for that long and would need to be cleaned out before using. That one looks like it would be worth the risk.

It looks to me to be an open bearing. Here is a link to the listing if you are interested in reviewing it for yourself.

This would cover my need for the 7307 bearing at the top of the quill, although I will still need to source a 7208 for the lower. I did find this, it seems to follow a similar story to the NTN bearing I found. I'm not overly familiar with RHP. A quick search showed that they were an English company absorbed into NSK at some point. Likely defunct now or fully absorbed into NSK as I can't find any current website or literature.

I did come across an NSK-RHP bearing designation document that indicates it is what I'm looking for to match the NTN. 15 degree contact angle ABEC 7/P4 accuracy. It feels like a faux pas to mix bearing manufacturers but since they're both held to the same accuracy standard I suppose there's no risk to it.

 

[Ischgl99]

Thanks, those pictures were better. That is an open bearing, the black part I thought could be a seal is the cage. The NTN is worth taking the chance, it looks like it is still in good condition. I don’t think there is any concern with mixing bearing brands in your spindle. Usually you would use the same brand when mounting back to back, or face to face, but since these are on opposite ends of the quill, I can’t think of any reason to get whichever brand you can find.

You are correct, RHP was an English company that got bought by NSK, not sure when either, but the bearings are high quality and were used in Bridgeports built in England. The RHP bearing should work fine, it’s a light preload when mounted with another, but that doesn’t matter in your case since they are at opposite ends of the spindle. I think both of those look like they will work.

 

[ChandlerJPerry]

I was able to take a look at the spindle again today and take some measurements with a micrometer. Unfortunately my micrometer does not have a .0001" scale so I had to rely on the macro photo function on my phone and a calibrated eyeball.

The good news is that I took measurements in several locations and it is damn close, if not identical. Making a calibrated eyeball measurement I would say there is maybe .0001" of wear to the spindle. I know that will effectively double to .0002 of runout but that is a figure I can live with. I am also hopeful that with numbers that low that there may be enough raised/undamaged areas of the bearing seat to allow it to center properly when installed with some loctite 660. Combined with the thrust washer over the damaged shoulder, I think this situation may be salvageable.

Here is a photo of the mic measurement from the undamaged area:


And the damaged area:


I want to deeply and sincerely thank everyone who has pitched in their thoughts and wisdom along this journey with me. It has been a huge help and put me in a much better position than I would be in had I not made this thread.

I think that next I am going to get those bearings ordered, along with some Kluber NBU 15 and a thrust washer. I will also replace the 6208 bearing just to be thorough, but I think I'll get a standard precision bearing because I don't see the point of making it precision.

Would anyone be interested in some further posts giving an update on how it turns out?

 

[extropic]

Would anyone be interested in some further posts giving an update on how it turns out?

Of course.

 

[ChandlerJPerry]

Popping in again while I wait on items to come in the mail to ask if anyone has any alternative nominations to Kluber Isoflex NBU15? As many can empathize, my hobby does not have a generous budget. If it's truly the best choice for my application, I will begrudgingly part ways with my money.

However when I look at the conditions it's typically specified for, it seems like it may be overkill. My spindle tops out at 2000 RPM and I can't imagine it would see anywhere near the load that a machining center would.

A couple options that came up in my search as possible acceptable substitutes are Lubriplate SYN GR-132, and Mobilgrease 28. I'm also a personal fan of Super Lube synthetic #2 grease for general purpose lubrication around the shop, so it came to mind as well. I would appreciate some insight on this. Especially from @Ischgl99 as I'm sure that lube selection is a major consideration in the bearing industry.

 

[Janderso]

Yeah, I agree with the Kluber. I researched it when I replaced the bearings on my B&S surface grinder.
I also used it when I replaced my spindle bearings on my big mill.

 

[Janderso]

You only need about 30% fill on the bearing. Over greasing can cause heating.

You beat me to it.
We aren't packing wheel bearings here.

 

[Ischgl99]

I’ll probably ruffle some feathers with this comment, but here goes. Kluber greases are very high quality, but NBU15 is meant for high speed spindles, such as found on machining centers. I do not think it is appropriate for knee or bench mills, so you will never find that in my machines. Viscosity is the most important criteria when selecting a grease or oil, at 15, the NBU15 is below what is needed at slower speeds, but appropriate for machines in the 10,000 rpm and higher range. The correct viscosity needs to be calculated based on a variety of factors, including bearing size, operating speeds, and operating temperature. If you live in a hot climate and your shop is not air conditioned, a higher viscosity grease might be necessary compared to me here in CT with my machines in the basement that never gets above 70f. If you spend half your time at 1,000 rpm, and the other half at 5,000 rpm, the viscosity requirements are different at each speed, you would want a grease that is suitable at both speeds. It’s ok to go with a higher viscosity, to a point, but you need to be above the minimum at the lower speeds if you want your bearings to last, and slower speeds require a higher viscosity than at higher speeds and temperatures.

Having said all that, mills in a home shop, or even a job shop, do not see hard service, so a wide variety of greases would be perfectly fine. I would not use less than a 32 viscosity. Bridgeport specifies an SAE10 oil for their spindles, that is equivalent to an ISO32 viscosity. If you want to go with a Kluber of the appropriate viscosity, go ahead, but anything from Mobil, Shell, Fuchs, etc of the right viscosity is going to work too. Kluber does have the advantage that it has fewer impurities than industrial greases, so there are benefits to using it in high precision bearings, just make sure you select the right one.

I have a Burke Millrite with tapered roller bearings. Max speed is 2,500 I believe. I went with Mobil SHC100 with a viscosity of 100 since I had it and have decades of experience with it, and I know the bearings will be properly protected at any speed I run my mill at. I could have easily gone with a grease with an oil viscosity of half that and still be fine, but I don’t know if there are any readily available. For a machine that runs at 5,000 rpm, I would look for something in the 32 range, 46 would be perfectly fine too if that is what you can find. It’s important to not overfill the bearings, and don’t regrease too often. More bearings fail from over greasing rather than under greasing, and the spindle will run hotter with too much grease. I do two or three pumps from my grease gun every 6 months or so, no idea how many hours yet since I haven’t gotten around to installing the hour meter.

Another warning, make sure you know what the base soap is in the grease before switching types. Some of the soaps are not compatible with each other and if you put incompatible soaps together, they can cause a failure of the bearing. If possible, fully wash out the old grease before using the new one.