Product category:
Bearings and guideways - rotary and linear
News Release from: The Barden Corporation | Subject: Bearing failures
Edited by the Manufacturingtalk Editorial
Team on 20 June 2003
Bearing failures attributed to faulty
mounting
Experience shows that up to one third of bearing failures can be attributed to improper handling and faulty mounting of bearings.
Experience shows that up to one third of bearing failures can be attributed to improper handling and faulty mounting of bearings Moreover, this problem promises to get worse as bearing tolerances become ever more exacting
This article was originally published on Manufacturingtalk on 12 May 2004 at 8.00am (UK)
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Today, precision bearings can work to tolerances of 1 micron, yet handling such bearings without protective gloves can place fingerprints on the bearing surfaces 13 microns high.
Dust particles are even worse, at 25 microns, and human hairs, relatively colossal, at 76 microns.
The implications of this for the bearing user are major changes to the way in which bearings, and precision bearings in particular, are handled.
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No more the traditional image of the greasy workbench with the ever-present hammer.
Rather, the clean room type conditions that prevail in electronics production.
The best approach is to regard every kind of foreign material - dust, moisture, fingerprints, solvents, lint, dirty grease - as abrasive, corrosive or otherwise potentially damaging to the bearing precision The problems with handling bearings begin the moment they are removed from their protective packages.
Because of this it is best not to remove them until they are ready for use, and then only after the work area has been effectively cleaned and prepared.
Once unpacked, the bearings should only be handled with clean, dry, talc-free gloves.
Here care should be exercised as material incompatibility between the gloves and any cleaning solvents could result in contaminant films being transferred to the bearings during subsequent handling.
Where the bearings are instrument types even handling with gloves should be avoided in favour of surgical tweezers.
With the bearings unpacked, they are now subject to atmospheric borne contaminants, so they should be kept covered at all times.
The cover should be clean and dry and of a type that will not shed fibrous or particulate contamination into the bearings.
Keeping bearings covered is an essential "do" in the lexicon of bearing handling.
An essential "don't" is to wash or treat the bearings prior to mounting.
These practices are unnecessary today, as companies like Barden take great care in cleaning bearings and properly pre-Lubricating them before packaging.
Another essential is to use only bearing-quality lubricants, and to keep them clean during application and covered between uses.
And, just taking a step back for a moment, remember to check that that all lubricants are within the recommended shelf life before application.
Finally, only apply the correct quantity of grease, as specified by the bearing manufacturer, and ensure that the applicator itself is clean.
Once these tasks are completed the bearing is ready for installation.
For this task (and for bearing removal) only use clean, burr-free tools that are designed for the job.
The tools should not be painted or chrome plated as these can provide a source of particulate contamination, which might ingress and damage the bearing.
The requirement for burr-free components also extends to all other parts of the bearing assembly, especially housing interiors and shaft seats.
These two areas should also be thoroughly cleaned before fitting.
Then, when fitting commences, care must be taken to ensure that bearing rings are started evenly on shafts or in housings, to prevent cocking and distortion.
Apply force only to the ring being press-fitted.
Never strike the outer ring, for example, to force the inner ring onto a shaft.
Such practice can easily result in brinelling of the raceway, which leads to high torque or noisy operation.
Finally, where interference fits are concerned, use heat assembly (differential expansion) or an arbor press.
Never use a hammer, screwdriver or drift, and never apply sharp blows.
Where the task is one of removing, rather than installing, a bearing the same strictures of cleanliness apply.
Ensure that all surrounding areas are clean before removal and, once removed, isolate and identify the bearings for record purposes, or re-ordering.
Alternatively, inspect the bearings carefully before re-use. Request a free brochure from The Barden Corporation ...
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