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03-02-2010, 07:33 AM #1
Ultrasonic cleaning OK for ball bearings?
I intended to replace all the ball bearings in my 50+ year old Hendey Tool & Gage lathe. After purchasing a few replacements, I though it might be more practical to clean and then inspect the old ones. Only those in bad shape would be replaced.
I have a small ultrasonic cleaner and it has worked wonders on small items. If an ultrasonic cleaner is used, do the individual balls vibrate against the cage and inner race causing microscopic pitting on the surface of the balls which ruins the bearing? This concern came about due to the warnings about not spinning dry bearings (after cleaning but before application of grease or oil). What would be a easily obtainable solvent for removing the old grease? I don't want to use anything containing methylene chloride.
Many of these bearings are shielded but with a felt washer. Was this a way of retaining lubrication and keeping out dirt 50 years ago before the introduction of rubber seals? Since these felt-containing bearings are difficult to locate, could sealed bearings of the same construction be substituted?
03-02-2010, 07:46 AM #2
I've done it, though I've felt "uneasy" after removing the bearing from the ultrasonic tank. The bearings often seem to come out kind-of "locked up". They free up immediately with the slightest movement, but it's something that makes me think it's not a good thing to do.
03-02-2010, 07:48 AM #3
I clean ball bearings in my ultra-sonic tanks, but you want to be careful about how long. I soak them in solvent first to loosen the gunk up and then run them in the tank for one or two minutes, no longer. I've never had a problem doing it this way. I think if you leave them in too much more, you will start to beat the races. The strength of your tank makes a difference too. A small bearing in a big tank won't take long because the action is pretty strong, but a big bearing absorbs a lot of the energy and will take a little longer to get clean.
03-02-2010, 07:49 AM #4
I've always been told it's a no-no.
But a friend of mine decided to service his fairly new (square head) Schaublin 102 lathe head and I walked in just after he'd cleaned the bearings "for a good hour" in the ultrasonic. I told him he was nuts, but that was ~5 years ago and the lathe has been in service ever since running at least 4 hours per day with no problems.
Personally, I wouldn't do it.
03-02-2010, 08:42 AM #5
In avionics we always cleaned instrument bearings in aforesaid cleaner.
Followed by a dunk in Alky, blow dry, (no spinning), lube, good to go.
03-02-2010, 04:27 PM #6
ultrasonic cleaning fluid
what kind of cleaning fluid to ultrasonic clean bearings?
most ultrasonic cleaners are not rated for flammable solvents. Caustic cleaners will remove organic material but the water rinse will rust steel. Caustic cleaners attach certain metals like aluminum. Some cleaning compounds are water and soap based and water will rust steel easily.
03-03-2010, 07:01 AM #7
I've read guys warning never to do it, but, I don't see how the impact forces in the tank are sufficeint to damage a good bearing (yeah, sure I've seen cavitation damage in cylinder liners and pumps - after hundreds of hours operation though!)
I can see how the flakes in a damaged bearing could be dislodged, or the gunk that was concealing a frosted ball or roller removed to reveal the damage, but I cannot see it damaging an ok bearing - I might be completely wrong though.
As to rust:
Rust will be minimised if you use water that has been boiled to de gas it. a couple drops of washing up detergent makes a good wetting agent.
I've dried bearings under halogen lamps and hung them on the hot lamp fittings too. no rust yet.
I've a couple of cheap US cleaners, and I've offered to clean my next door neighbours fuel strainer gauze off his tractor, next time the tank is empty. I'm planning to do it with petrol, and site the cleaner well away from the bulding, and switch on and off from the safe end of an extension lead. if it catches fire, so be it. I can dump damp sand on it and it will be no great loss.
03-03-2010, 07:28 AM #8
I'm always trying to save and reuse; I've thought about this quite a bit and have talked to professional spindle rebuilders about it. The safe advice is don't do it. There are a lot of variables like the size and power of the tank, the cleaning solution, the time and how much abrasive is present. At work we easily frost glass beakers that contain some grit, so you want to wash as much crud off the bearings as possible before using the ultrasonic. I have a big multi-hundred watt tank and have to be very careful. A small cleaner is less risky. IMHO, 5-10 minutes should be the maximum time. I manually clean with solvent, then use detergent in the ultrasonic. AFAIK, none are really rated for flammable solvents. A well used bearing has probably seen a lot of contamination and I doubt the ultrasonic is going to do anything worse. I wouldn't take an expensive brand new bearing and subject it to ultrasonic cleaning.
03-03-2010, 08:52 AM #9
I've cleaned many hundreds of bearings from chainsaws and other 2 stokes in ultrasonic cleaners. These operate at 10-14Krpm... Also, a lot of mill, lathe, transmission spindle and other bearings. Never an issue and I inspect the races and balls with an otoscope. I have several cleaners - one has 8 transducers and can clean very aggressively, but I tend to not to use this for the more delicate stuff.
Most important - keep the bearings off the bottom of the tank - most buzz like crazy at frequencies much lower then the ultrasonic. I suspend mine in a mesh bag or on a wire.
The real question is why? I use it because of the caked combustion products on the crank bearings. Most machine tool bearings will have little that cannot be removed with clean solvent. Unless the ultrasonic tank solution is clean, you're likely putting more junk back into the bearing.
Before anything else, I flush all bearings with CRC Brakleen - just tetraflourethelyne (sp?). and a light air flow (no fast spin). A quick otoscope inspection will reveal if the bearing needs further cleaning.
Although it's not recommended for all the usual reasons, I often use Coleman lantern fluid as a solvent cleaner - it shows no tendency to foam or boil. Mostly I use clean water with a dash of ammonia and detergent. A quick dip in WD40 and a light blow off will stop flash rusting. Then, another spray with Brakeen, blow dry and a light lube.
03-03-2010, 09:54 AM #10
Tetrafluorethylene is a gas that is polymerized to make PTFE (Teflon(R) and other brands). You wouldn't be able to buy TFE over-the-counter AFAIK. Nor would you want to: it can polymerize pretty explosively.
03-03-2010, 10:06 AM #11
There are two different Brakleens. The one you refer to is the "NON-chlorinated" version which I do not use...
This is the version I use - no issues with residue or cage materials:
CRC Industries Automotive Product Detail
It's found in the RED (not "green" - what a joke considering the contents ..)) aerosol or buy it in the gallon contianers. Here's the MSDS :
And.. I meant to say Tetrachloroethylene.... I knew I had that wrong...
03-03-2010, 12:13 PM #12
note: you may have to weigh down the pan if the part/solvent is small. i keep a few chunks of metal around (clean) when that is necessary.
03-03-2010, 12:27 PM #13
03-03-2010, 01:31 PM #14
We used a dedicated cleaner and rinse, trade name is L&R.
We cleaned bearings down to about 1/4" O.D. (Ball bearings).
03-03-2010, 02:32 PM #15
03-03-2010, 02:46 PM #16
I don't know what to think. I've heard pro and con about U/S cleaners and ball bearings. I used to work in a Naval Shipyard and no-one is as paranoid about noisy bearings as the US Navy especially when it came to subs. The shipyard had a dedicated beariing section where all incoming bearngs destined for sub service were inpected for compliance and noise signature.
They had a gadget called an anderometer that looked like an old fashioned record player. It spun the inner race and a pickup registered the noise on a meter and amplified it for a speaker. The tech could shift load direction merely by manipulating the outer race. Pretty slick and simple and no significant noise problem could get past it.
They also had a fancy no-damage way to remove the shields and seals, the cage, etc. They could chill the inner race while heating the outer race thus angular contact bearings could be made to fall apart without trauma. They could check balls for size and sphericity, had elaborare cleaning facilities including U/S. The cleaning fluids of choice was Freon 111 - probably unobtianable by now - and a propritory petroleum solvent called "Agitene" and a waterbased caustic called "Oakite." The Freon was used in the U/S cleaner and only on separated components; never an assembled bearing.
Here's the finding: U/S cleaning will cause "fretting" damage to ball (and roller) and races of bearings. The fretting under magnification appears as crystaline pits in the race and ball finish at impingement sites. They are tiny but increase in size with exposure to U/S agitation and, having sharp edge, they form sites for cavitation bubbles potentiating further erosion. The fretting damage takes far longer in petroleum solvent that in aqeous U/S baths - I presume because petroleum solvent cavitation is far less energetic than in water.
Next question is will the fretting damage interfer with with the bearing's operation. Well I think it would depend on whether the damage was in the loaded ball path. Normal bearing failure is through race fatigue. Surface defects develop into cracks from high unit force loading as the balls roll by. Cracks propagate and merge following the loading. When the cracks meet sone distance under the race surface little flakes separate leaving a pit. Pit follows put until a continuous line develops meanwhile the bearing's noise signature increases until the fillings fall out of the teeth of whoever has to listen to the racket. If the fretting damage lie slightly ut of the loaded ball path U/S cleaning will do little harm but how do you ensure this won't happen?
It's illegal in the US Navy to U/S clean an assembled rolling element bearing but there is no restricton for individual separated componants. It aint the U/S cleaning process, it's the high frequency component impingement that does the damage.
I reccommend the Navy method of cleaning bearings. First remove one shield if necessary and use pressure flushing with warm, clean, filtered perrolem solvent (I prefer Agitenes but the Navy references Diesel) after manually debulking the existing grease charge. Placing the bearing under the solvent flow for long periods of time and repositioning it from every 15 minutes will clean the bearing more effectively than scrubbing it endlessly (shedding bristle fragments into the crevises). A carbonator pump and a zerc fitting with the ball and spring punched out for a nozzle makes a nice high pressure solvent lance but the splash and splatter make it necessary to build a little glove booth to contain it.
It's hard to beat assemblies that are completely clean of grit and contamnants lubricated with clean oils and greases. Their reliability is amazing.
03-03-2010, 03:06 PM #17
Thanks for the info. I happened to work at DuPont in the Fluorocarbon business unit, so I probably was overly sensitive to the mention of TFE.
Does the TCE version give you better results than the naphtha version? I think it's the naptha version you get at Walmart, right?
03-06-2010, 06:03 PM #18
PERC (Red can version) is one of the best degreasers/cleaners you can get. I buy it in 1 gallon containers - many times cheaper than spray cans, and you can reuse it.. I use "dip/soak", then small quantities of the spray can version - for a very clean flush.
The Naptha/acetone/IPA version is "non-chlorinated" - to meet the new "green" rules of some States. If I want a low volitilty napha product I use the current version of Coleman lantern fluid. I can add my own IPA etc as requried.
For cleaning the "green" versions are "o.k.", but comparatively poor on congealed and gummed products. I have concerns about acetone and some non-metallic bearing cage construction. So long as it's legal (it is in my state) I'll continue to use the original product.