Lubrication & Relubrication

Bearing lubrication is primarily intended to reduce friction and wear of the bearing, but also serves a variety of other purposes such as heat dissipation and corrosion protection. There are three main categories of lubrication: grease, oil, and dry-film lubricants.

Open Bearings shipped without grease are coated with a MIL-PRF 6085 preservative oil. This is intended to protect Silverthin bearings from corrosion but is not intended for operation. Silverthin recommends that bearings be cleaned and relubricated prior to use.

Sealed Bearings are shipped ready for installation with the external surfaces of the bearing protected using a light layer of the grease used for lubrication. Unless otherwise requested sealed bearings are greased with a 20-30% fill of MIL-G-81322 general purpose grease. Shelf life for sealed bearings is generally 2 years, after which the bearings should be serviced or returned to Silverthin for relubrication.

Grease is the appropriate choice of lubricant for most applications. Grease has less tendency for migration which allows for a simpler/lower profile design and often allows bearings to be “lubed for life”. Silverthin sealed bearings are always supplied with grease.

Oil can support much higher bearing speeds, but usually requires a more involved lubrication system. The general rule is that the bearing should not be fully submerged and that the oil level should only reach the midpoint of the lowest rolling element when mounted vertically.

Brand Name	Basic Type	Operating Temperatures In Fahrenheit	Uses
Royco 885 (MIL-PRF-6058D)	Synthetic Oil	-65 to +250	Silverthin’s Open (un-sealed/un-shielded) bearings are dipped in this oil as a corrosion inhibitor (not intended to be a lubricant). You must grease or oil the Open bearings for your application. Light general-purpose oil
Windsor L-245X (MIL-L-6085)	Synthetic Oil	-65 to +300	Low torque
Beacon 325	Synthetic Grease	-65 to +250	General purpose grease Low torque
Royco 27 (MIL-PRF-23827)	Synthetic Grease	-100 to +275	Corrosion resistant Heavy loads and high speed
Rheotemp 500	Synthetic (Non-silicone Grease)	-65 to +350	Oxidation inhibitor High temperature and high speed
Mobil 28 (MIL-PRF-81322)	Synthetic Hydrocarbon Grease	-65 to +350	Silverthin Sealed or Shielded bearings are supplied with this grease at 20-30% fill. Low torque Low speed oscillation
SRI-2	Mineral Grease	-20 to +350	Long life. Water resistant. High speed and high temperature.
Krytox 240AC	Fluorinated Grease	-30 to +550	High temperature
Multitemp SRL	Synthetic Grease	-40 to +300	Very quiet Low torque
Braycote Micronic 601EF	Perfluorinated Polyether Grease	-112 to +400	Low pressure/vacuum environments Hostile chemical environments
Aeroshell 33 (BMS3-33)	Synthetic Grease	-100 to +250	Corrosion resistant Heavy loads

Dry-Film Lubricants are typically considered only when environmental considerations prevent grease or oil from being appropriate. Dry-lubes commonly used include dicronite (WS2), graphite and MoS₂ platings. Dry-film lubricants have drawbacks of excessive particulate generation which may cloud optics or other sensitive components if not taken into consideration.

Some of the Dry Lubricants are as follows:

A dry lubricant is used as a solid lubricant but can also be used as a Specialty Coating. Visit our Speciality Coating page to learn more.

Tungsten Disulphide (WS₂) coating has dry lubrication and reduced friction properties, is non-toxic and has corrosion resistant properties. It is applied as a powder that is adhered to the bearing. This coating was originally developed for space applications, is approved by NASA, and is commonly used for space and other vacuum applications. It has a uniform thickness of 0.0005” and can be used for a wide temperature range of extreme cold (-325°F) to extreme heat (850°F in atmosphere, 1400°F in vacuum). For use in bearings a maximum contact stress of 350ksi is recommended. WS₂ is silver in color when applied.

Molybdenum Disulphide (MoS₂) coating has dry lubrication, reduced friction and corrosion resistance properties. It has uniform thickness of 0.0002” and can be used for a wide temperature range of extreme cold (-325°F) to extreme heat (750°F). For use in bearings a maximum contact stress of 250ksi is recommended. MoS₂ is silver in color when applied.

PTFE coating has dry lubrication, reduced friction, corrosion resistance and insulating properties. It also has increased resistance to fretting and fretting corrosion and performs well in vibratory applications. It has uniform thickness of 0.0008” and can be used for a maximum temperature of 500°F. For use in bearings a maximum contact stress of 150ksi is recommended

Graphite is primarily used as a dry lubricant, but can also be contained in oil. It is primarily used to reduce friction. It works well when water vapor is present as it helps the graphite bond to the bearing surfaces. Graphite is effective at temperatures as high as 850°F and even higher temperatures for intermittent exposure. It is not effective for vacuum or space applications.

Selection of the correct lubricant is entirely application driven and should consider the following:

Desired bearing speeds
Bearing loads
Limiting torque development
Intended service intervals
Dithering or oscillating rotation
Environment considerations such as:
- Temperature extremes
- Vacuum applications
- External Radiation
- Chemical interactions
- Water washout or miscibility with other liquids

Silverthin bearings can be shipped with alternative lubricants and custom fill amounts to support your application. Silverthin accomplishes your custom lubricant needs within our on-site assembly processes where cleanliness can be controlled and other specialized lubrication processes can be performed in our ISO Class 6 Clean Room. Some of these other specialized lubrication processes may include grease plating, vacuum impregnation of ball retainers and much more.

Lubricant selection can have a large impact on performance, cost, and lead time. Please contact Silverthin Engineering for lubricant review and product suitability.

Relubrication

Relubrication isn’t just a routine procedure-it’s the rejuvenation of your bearings, needed in order to continue operating at their peak performance. At the Silverthin Bearing Group of the Mechatronics Corporation, these relubrication services are performed in our ISO Class 6 Clean Room. Our Clean Room is ISO Class 6 certified by a third party as well as by many of the bearing industry’s leading manufacturers.

Within our certified Clean Room, we stock the standard grease and oil options talked about in the Lubrication section above, as well as hundreds of specialty and high performance lubricants, including MIL-spec, food grade, high-vacuum, corrosive resistant, and low out-gasing to support all of your lubrication needs.

Why Lubrication Matters

Maintain Peak Performance: Proper lubrication minimizes friction, ensuring your bearings operate smoothly and efficiently.

Extend Bearing Lifespan: Regular relubrication can significantly reduce wear and tear, prolonging the operational life of your bearings.

Prevent Unexpected Downtimes: A well-lubricated bearing is less likely to face unforeseen issues or breakdowns, ensuring uninterrupted operations.

Shelf Life: Ensures the lubricant’s longevity matches your operational needs.

Our ISO Class 6 Clean Room environment includes, but is not limited to the following:

Relubricate and refresh expired bearing inventory
Specialized lubrication processes
Complete documentation and traceability for all orders
Extensive range of lubricant options
Small and large volume orders accepted
ISO Class 5 flowbench environment also available for higher precision products