Bridgeport Spindle Bearings

[fastblackss]

Hi all,

Just replaced the spindle bearings in my Bridgeport boss 5 cnc. Old bearings were very noisy, got a matched set from H&W.

Watched video and read instructions thoroughly, changed the bearings with no issues. Packed the bearings with grease supplied with bearings, says not to over pack. Bearings came with a small tub of grease, packed both.

Installed, fired up machine and quiet as can be.

Ran machine for about 45 mins for a cnc program i have and spindle was very warm/hot when done. Took it back apart, double checked my install, see nothing wrong.

What can be causing all this heat? It’s definitely in the spindle area, never got hot before, I’ve ran this machine for quite some time so this is def a new problem with the bearing swap. Too much grease? Not sure how that makes it hot but I need this machine to work for me. Any suggestions are appreciated.

Thank you, Dave

 

[4GSR]

Yep, packed them with too much grease. I don't know the exact quantity in cc's. Someone here will chime in and speak. I did the same thing on my Index 645 mill twenty years ago. Ran hot in the high RPM's. It took about 5 years for all of the excess grease to make it's way out of the spindle. It does run cooler with lessor amount of grease in the bearings. I'm sure on the Boss mill spindle, it's sealed at the bottom of the spindle to prevent grease from escaping.

 

[fastblackss]

Thank you for the response. Yea the bottom has a dust shield so grease really won’t come out. Guess I can pull it back apart and take some more grease out!! I don’t feel like they are packed solid but i greased them up well.

 

[4GSR]

The old rule of thumb used to be not to pack them with more than 30% volume of grease. Now, how to figure that, it's surely hit and miss IMO. Be surprise how little amount of grease will go a long ways in bearings.

 

[fastblackss]

Took it apart this morning, blew out a lot of the grease, put it back together and she’s still getting hot.

Any other tips? I can blow some more grease out I just think it’s odd that grease causes heat! Thanks for the advice so far!

 

[EmGo]

Took it apart this morning, blew out a lot of the grease, put it back together and she’s still getting hot.

Depends what you think is hot ? Your hands are pretty sensitive, ya know. They'll pick up a fairly low temp and think it's hot. Try a thermometer.

You can also run it in slowly, like give it a few hours at lower rpm, then go faster, then faster, etc etc.

You may still have too much grease, it's the churning that makes heat, and you'd be surprised how little grease you want, but unless it's getting really hot, not just hot-to-touch, you're not going to hurt anything. Spindles always run pretty warm.

 

[fastblackss]

I mean it’s definitely warmer than before.

After running 45 mins, I can hardly touch the quill.

 

[4GSR]

What size bearings are you using? Are you aligning the marks on the bearings to each other when you are assembling? What grade/specifications grease are you using? You made the comment that you blew out the excess grease. Did you do this with compressed air? What methods did you use to assemble the spindle and bearings. How fast were you spinning the bearings? The list goes on and on...

 

[fastblackss]

What size bearings are you using? Are you aligning the marks on the bearings to each other when you are assembling? What grade/specifications grease are you using? You made the comment that you blew out the excess grease. Did you do this with compressed air? What methods did you use to assemble the spindle and bearings. How fast were you spinning the bearings? The list goes on and on...

Bought the bearings from H&W, nsk super precision bearings with grease they supplied. I believe they use a Mobil 1 grease, just came in a little tub unmarked. Yes marks on bearings are lined up. Yes, used some compressed air to get rid of some grease. I have a shop press to disassemble and reassemble. Bearings were not damaged ever, I took my time. Spinning machine 3500rpm. Thanks

 

[jccaclimber]

I'm assuming the boss spindle is the same general design as the Series 1 spindle, to bearings with spacers between them and then another bearing up top?
If that's the case, the two spacers should be the same height. I mention this because on at least two of the spindles I've seen apart they were *not* the same height. I've gotten differing stories from rebuilders about this. Some said BP sometimes used offsets in those instead of or in combination with offsets in the bearings, others said it was to make a different than stock preload. Lastly I'm told it could have been some hack's solution to putting more life into old worn bearings. I'm a bit suspicious about this last one being remotely common, but it was told to me in the voice of someone who seemed to have done so once before. Did you verify that your spacers are in fact equal height, still have parallel ends, etc?

Edit, have you called H&W back to see if they have any additional advice?

 

[EmGo]

After running 45 mins, I can hardly touch the quill.

106* will do that. Really, a thermometer is a lot more accurate than your fingertips.

 

[Stradbash]

Mobil 1 grease is pretty stiff compared to the high quality spindle greases I've used.
I'll suggest watching this video and seeing if there are any things you'd like to do differently the next time...

I look forward to hearing of your results!

Good Luck!

 

[Conrad Hoffman]

IMO, grease or preload would be the only things I'd expect to cause this. 3500 RPM is slow as slow, so something's really not right.

 

[AlfaGTA]

Did not read that you did any “run in” of the spindle upon fitting the new bearings.
I would expect a new install would start at very low RPM (like 100 RPM ) and running there for some time ( like 20 min)
Then increasing the RPM (maybe 250) and run for another 20 min
Rinse and repeat in steps.

I have a Harrison factory tech sheet for new spindle bearings on their 1330 CNC lathe. Process takes like 4 hours to get to max RPM (3500)

My Deckel FP4NC vertical spindle runs warm. Bearings produce heat if they are doing work. Preload produces heat. No preload, no tool control.
Deckel factory says spindle temp of 130*f is OK.

Your old bearings were worn, less preload= no heat.
Ask the seller about the length of the bearing spacers for their bearing pack.

Cheers Ross

 

[4GSR]

My little dinky Index 645 mill, the bearings would run extremely hot if I was to run it at 3500 RPM, too! Hardly ever push mine over 2K RPM. Of course, it's a manual mill, not CNC like the boss is. They were packed with Lubriplate grease. I don't remember the grade. I've since started using a Mobil grease that is a pale red/pinkish color in the spindle rebuilds I did on my K O Lee T & C grinder a few years back. Mobil recommended it for high speed bearings on their web site. Those bearings never did produce any heat when touched.

 

[Jhn3:16]

AlfaGTA (Ross) nailed it! You certainly need to do a "run in" on the new bearings. Typically you would want to run it in both directions (for/rev) at each RPM interval.
This gives the grease a chance to spread evenly, that is if there is not too much and it has some place to go

Brandon

 

[LexD]

H & W have a you tube video showing how they replace spindle bearings, the presenter in the video does mention that bearing spacers should both measure the same height and he shows how he confirms the measurement with a simple micrometer measurement but does not empasize the fact that these spacers need to be parallel to less than .0001", for optimal performance of the precision angular contact bearings, as per the bearing manufacturers specification.

Before refitting used spacers they should also be checked for damage or burrs and lightly stoned with a precision ground flat stone.

The height of the inner spacer in relation to the outer spacer can be varied slightly to change preloads, this information is also available in bearing manufacturers catalogues.

 

[jccaclimber]

In the video H&W says "Exactly the same". In that context I interpreted it as identical on a device reading at least 4 decimal places in inches. Unless you're also parallel to 0.0001" you're not going to read the same to 0.0001" at all locations on both rings. It would have been good of them to measure a couple more locations, though I generally expect people know rings are not just defined at one location.

 

[LexD]

In the video H&W says "Exactly the same". In that context I interpreted it as identical on a device reading at least 4 decimal places in inches. Unless you're also parallel to 0.0001" you're not going to read the same to 0.0001" at all locations on both rings. It would have been good of them to measure a couple more locations, though I generally expect people know rings are not just defined at one location.

Your interpretation is different to mine.

 

[mottrhed]

Excessive heat is typically created by too much or too little grease, too heavy or lack of preload, misalignments, and possibly overloading (belt tension or other outside force).

In this case, assuming you have the "right" bearings, set at the right preload, and spacers-shoulders-journals-housings all are in spec (which is a lot to assume), you likely have far too much grease. Looks like you are using nsk bearings, the publish the exact amount of cc fill for a particular bearing. You can find it in their catalog, or if you give me the bearing part number I can tell you if its the right thing and what the grease fill is.