Bridgeport Spindle Bearings

[jccaclimber]

Your interpretation is different to mine.

Do you:
1. Not feel envelope principle applies if a drafting standard is not explicitly called out?
2. Can you think of a geometry I may not have where you meet the identical height but requirement but not the parallelism?
3. Do you think "Exactly the same" on the micrometer is satisfied by a looser tolerance, such as nearest 0.001"?\
4. Something else I've not thought of?

 

[eKretz]

Lots of guys seem to be talking about excessive heat. We don't know whether that is even the case yet without quantitative measurement. OP, get a thermometer on the thing and tell us what the temp actually is. Without that we are all pissing in the wind.

120° F at top speed is just fine, even up to 130° is okay but getting up there for me. I changed the spindle bearings in my Wells Index not too long ago; did the full break-in from low speed up to high in steps. Forward and reverse. Temperature at the end was around 115° F and stable after 30 minutes at 4,000 RPM. Perfect.

You can find the recommended break-in procedures for bearings in several manufacturers' bearing catalog/manuals. Generally you start low and run for a prescribed amount of time, then check temp. If it's okay, you move to the next speed and repeat. If temp is too high you back down a speed and run that step again, then bump up and try again. So on and so forth until you're topped out.

 

[CarbideBob]

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

NO

 

[EmGo]

NO

Are you sure ? Lumley Spindle Service, rebuilt excello and heald spindles up in your neck of the woods, made a point of the fact that they ran rebuilt spindles in for such-and-so time after a rebuild ... (I forget how long ... an hour? )

 

[LexD]

Do you:
1. Not feel envelope principle applies if a drafting standard is not explicitly called out?
2. Can you think of a geometry I may not have where you meet the identical height but requirement but not the parallelism?
3. Do you think "Exactly the same" on the micrometer is satisfied by a looser tolerance, such as nearest 0.001"?\
4. Something else I've not thought of?

I know, through experience, that other peoples interpretation of "exactly the same" is not the same as mine, especially when measuring sub .0001".

 

[CarbideBob]

Are you sure ? Lumley Spindle Service, rebuilt excello and heald spindles up in your neck of the woods, made a point of the fact that they ran rebuilt spindles in for such-and-so time after a rebuild ... (I forget how long ... an hour? )

YES I am sure.
Any spindle rebuild needs a run-in test for temps. This is to tell you if if all went together right.
Weird thing here to rookies is that there has to be a nice smooth temp rise on the run trial. Too low a temp rise is just as bad as too high a temp as a warning sign.
Somewhere around 5-10% of the product will not pass.
Which means take apart and find out why. At that point you know you are losing money on this rebuild.
This is why spindle guys are so anal about fits, stoning, blue and hand scrape nuts, grease load, clean room and super clean the parts.
Yes I do know Lumley and they have done some of my spindles a ways back.

 

[eKretz]

YES I am sure.
Any spindle rebuild needs a run-in test for temps. This is to tell you if if all went together right.
Weird thing here to rookies is that there has to be a nice smooth temp rise on the run trial. Too low a temp rise is just as bad as too high a temp as a warning sign.
Somewhere around 5-10% of the product will not pass.
Which means take apart and find out why. At that point you know you are losing money on this rebuild.
This is why spindle guys are so anal about fits, stoning, blue and hand scrape nuts, grease load, clean room and super clean the parts.
Yes I do know Lumley and they have done some of my spindles a ways back.

I'm with you on this, but can you explain why you said "NO" on the other quote? It sounds like you agree with what was said by Ross unless you were just disagreeing on the second quoting post's "give the excess grease somewhere to go" thing. Which I'm also with you on.

It's worth noting that too much grease can actually trash a bearing. If the rollers/balls start to skid instead of spinning, both they and the race will rapidly wear. Grease fill is important.

 

[EmGo]

can you explain why you said "NO"

Confused me too. Don't be gettin a swelled head, Bob. That's easy to do.

 

[AlfaGTA]

I can produce a copy of the Harrison factory new spindle bearing run in procedure if it maters....They might have been guessing, don't know.
Done a number of Deckel spindles and I always run them in, maybe i was fooling myself, but figured a little caution was better than not.
Cheers Ross

 

[Conrad Hoffman]

I've always run in precision and higher speed bearings. Question is, what does it actually do? Distribute the grease properly, especially a channeling grease? Actually change the surface finish of the balls and races? Seems anything like that is degradation, but maybe they get smoother?

 

[eKretz]

RUN-IN PROCEDURE FOR GREASED BEARINGS

A proper run-in procedure will provide the following results:
• Expel the excess grease found in the system
• Orient the lubricating film on each contact surface
• Establish a low equilibrium operating temperature
• Achieve a sealed-for-life lubrication condition

From one of the bearing manuals in my collection.

As long as the grease is not excessive in volume and trapped, I can see it helping to move *some* out of the way. Higher speed spindles need less grease than lower speed ones. Same manual says 25%-40% fill for <500,000 DN and 15%-20% fill for >500,000 DN. (DN = bore in mm × RPM). Most of the precision bearing manuals I've read say about the same thing in this regard.

 

[EmGo]

Higher speed spindles need less grease than lower speed ones.

The really high speed red heads didn't use grease or oil - they blew oily-mist air through the spindle bearings.

And high-speed gears use really light oil - on the outgoing side of the mesh

Lots of grease ain't always good.

Waiting for Carblob to come back and clear up the confusion he left on the carpet ...

 

[eKretz]

Yeah, but we were discussing a greased bearing. You are right that super high speed stuff is oil or oil mist. Carries away the heat way better, and a chiller can be used to cool it down.

 

[jccaclimber]

Now you guys have me curious. I'll have to see if there's any oil input on the spindle air bearings for my buddy's diamond lathe. If there is any oil on the input there must be a filter to clean it on the outgoing side. Of course that machine wants temperature controlled air on the input as well, wants to have the spindle balanced VERY well per setup, etc.

 

[jccaclimber]

I've always run in precision and higher speed bearings. Question is, what does it actually do? Distribute the grease properly, especially a channeling grease? Actually change the surface finish of the balls and races? Seems anything like that is degradation, but maybe they get smoother?

I've been told there is some extremely slight burnishing of the races, in addition to grease distribution. While perhaps not used on high accuracy bearings, some lubricants (namely the PTFE based ones) have "chunks" of solid lubricant in them. The really big chunks get broken down a bit, and you'd rather do that in lower load circumstances. As to what other mechanisms there are, I'm curious too.

 

[Conrad Hoffman]

Somewhere I read that the people who make Teflon powder say it has no benefit when added to grease or oil. IMO, greases with Teflon and/or moly shouldn't be used with precision ball bearings.

 

[mottrhed]

Now you guys have me curious. I'll have to see if there's any oil input on the spindle air bearings for my buddy's diamond lathe. If there is any oil on the input there must be a filter to clean it on the outgoing side. Of course that machine wants temperature controlled air on the input as well, wants to have the spindle balanced VERY well per setup, etc.

Are you saying this lathe uses air bearings? Thats a whole different animal, and if it is, there is no oil in an air bearing. But since im 99% sure thats not what you actually mean, no Ive never seen a collection system for an oil mist or oil injection system--(outside of makinos under race lube system)... It is atomized, ran through the spindle and released to the atmosphere. Naturally some machines have mist collectors, which would pull in some of this, many do not.

 

[eKretz]

Now you guys have me curious. I'll have to see if there's any oil input on the spindle air bearings for my buddy's diamond lathe. If there is any oil on the input there must be a filter to clean it on the outgoing side. Of course that machine wants temperature controlled air on the input as well, wants to have the spindle balanced VERY well per setup, etc.

Air bearings aren't going to use oil. It will be clean air filtered and dried before it ever gets to the bearings or they will clog. We're taking about rolling element bearings.

 

[jccaclimber]

Are you saying this lathe uses air bearings? Thats a whole different animal, and if it is, there is no oil in an air bearing. But since im 99% sure thats not what you actually mean, no Ive never seen a collection system for an oil mist or oil injection system--(outside of makinos under race lube system)... It is atomized, ran through the spindle and released to the atmosphere. Naturally some machines have mist collectors, which would pull in some of this, many do not.

No, not at all. All the talk of misted oil going into high speed systems got me curious on a tangent. Please disregard.

 

[John Garner]

I'm inclined to think that the supplied-by-bearing-dealer grease is more probably one complying with MIL-PRF-81322 general-purpose aircraft grease than it is an automotive wheel-bearing-and-chassisj "red" grease. The first MIL-PRF-81322 grease that comes to mind is Mobilgrease 28, and it is indeed dyed a deep red.

Exxon/Mobil's product data sheet says this about industrial application of Mobilgrease 28: "Mobilgrease 28 is also recommended for industrial lubrication, including sealed or repackable ball and roller bearings wherever extreme temperature conditions, high speeds, or water washing resistance are factors. Typical industrial applications include conveyor bearings, small alternator bearings operating at temperatures near 177ºC (350ºF), high-speed miniature ball bearings, and bearing applications where oscillatory motion, and vibration create problems."

That said, the observed heating is much more likely to be caused by over-filling the bearings with grease or excessive pre-loading than by the differences between Mobil One and Mobilgrease 28.