Proper bearing lubrication is vitally important to the optimal operation and life of miniature bearings. There are several common lubricants and hundreds of specialty lubricants that have been specially formulated to meet design requirements and the demands of various applications. The many available oils and greases are designed to lubricate the sliding contact between bearing components, protect the finished surfaces of the bearing from corrosion, provide a sealing barrier against contamination and in some cases, carry away heat. Miniatures bearing rolling contact surfaces are manufactured out of alloy steels to tolerances and geometries nearing one millionth of an inch. Normal wear and damage due to sliding contact, corrosion, contamination, and heat will accelerate in the absence of proper lubrication reducing bearing life significantly.
The following information can be used as a reference for lubricant selection and specification in general applications that fall well within bearing and lubricant ratings. For lubricant selection on bearings and applications with special characteristics or requirements please contact NPB for design and engineering support.
Windsor L-245X, Fuchs Lubricant Co., (MIL-L-6085 and MIL-PRF-6085)
Windsor L-245X is synthetic light Ester oil with an extremely low base viscosity (11.8 cSt at 40C). This lubricant is used in a wide variety of applications from aerospace and medical instruments to hobby applications. It is most commonly specified where minimal starting and running torque are requirements and low heat or loads can be expected. The pour point of Windsor L-245X is -65C with a flash point of 227C. This oil is specified for many applications required to meet MIL-L-6085 and MIL-PRF-6085. It is best suited for applications that fall within a temperature range for -57 to 177C. Windsor L-245X also contains a corrosion inhibitor and is often used as a protective coating for chrome steel bearings.
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Krytox 143 AC, DuPont
Krytox 143 AC is a synthetic, relatively thick, Fluorinated oil with a high base viscosity (243 cSt at 40C). This oil is clear, colorless, non-reactive and non-flammable. Krytox 143 AC is best suited for use in high temperature applications and can be used in hostile chemical environments. It is also suitable for some low pressure environments and space applications. The temperature range for Krytox 143 AC is wider than some bearing metals -34 to 288C.
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Beacon 325, Exxon Mobil
Beacon 325 is a Lithium grease with a light Ester oil base that smooth and buttery in texture and beige in color. Beacon 325 is a non-channeling grease with an NLGI grade of 2. This general purpose grease can be used in a wide variety of applications, but is generally considered advantageous where low torque is a consideration even at low temperatures. Beacon 325 also has excellent oxidation stability for the extended grease life needed in lube for life applications. The operating temperature range for Beacon 325 is -50 to 120C.
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Royco 27, Anderol (MIL-G-23827 and MIL-PRF-23827)
Royco 27 is a Lithium grease with a diester oil base that is smooth and buttery in texture and tan in color. Royco 27 is a non-channeling grease with an NLGI grade of 2. This lubricant is intended for use in high load as well as high speed applications. Royco 27 has a number of additives for oxidation and corrosion resistance as well as wear protection. This oil is specified for many applications required to meet MIL-G-23827 and MIL-PRF-23827C. The operating temperature range for Royco 27 is -73 to 135C.
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Rheotemp 500, Nye Lubricants
Rheotemp 500 is a Sodium complex grease with a synthetic Ester oil base that is smooth in texture and bluish-black in color. Rheotemp 500 is a non-channeling grease with an NLGI grade of 1.5. This lubricant is designed for use in high speed applications where wide ranges of operating temperatures are expected. Rheotemp 500 contains anti-oxidation additives. The operating temperature range for Rheotemp 500 is -65 to 350C
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Mobil 28, Mobil (MIL-PRF-81322)
Mobil 28 is a combination of synthetic Hydrocarbon fluid and clay thickener that is smooth and buttery in texture and dark red in color. Mobil 28 is a non-channeling grease with an NLGI grade of 1.5. This grease was designed for aerospace applications where high speed oscillation, low wear, high friction reduction, and low lubricant friction losses are required. Common applications include, airframe control bearings, motor applications, and high-speed instruments. Because of the clay thickener Mobil 28 is not recommended for instruments or motors where extremely low noise or extremely smooth operation are required. This grease is specified for many applications required to meet MIL-PRF-81322. The operating temperature for Mobil 28 is -54 to 177C.
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SRI-2, Chevron
Chevron SRI-2 is a Polyurea grease with a Petroleum base oil that is smooth and buttery in texture and dark green in color. Chevron SRI-2 is a non-channeling grease with a NLGI grade of 2. This lubricant is often used in high speed applications where water washout is a consideration, such as medical and dental instruments. Light fills of this grease, or application using a dilution and plating process can facilitate higher speeds and lower starting torque where required. The operating temperature for Chevron SRI-2 is -29 to 177C.
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Krytox 240 AC, DuPont (MIL-G-27617C)
Krytox 240 AC is a Fluorotelomer grease with a Fluorinated oil base that is smooth and creamy in texture and white in color. Krytox 240 AC is a non-channeling grease with and NLGI grade of 1.5. This grease is specified for many high temperature applications and in applications where lubricants are required to meet MIL-G-27617C. The operating temperature for Krytox 240 AC is -35 to 288C.
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Kyodo Multemp SRL, Kyodo Yushi
Kyodo Multemp SRL is a lithium thickened grease with a polyol ester and diester oil base. The lubricant is smooth and creamy in texture and slightly transparent off-white in color. Kyodo SRL has an NLGI grade of 2.5. This lubricant is a high-grade high-performance low-noise grease that also provides excellent low-temperature starting torque and provides long life over a wide working temperature range. Kyodo SRL is used in applications ranging from hard disk drive spindles to medical pumps.
The operating temperature range fro Kyod Multemp SRL is -50 to 150C.
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Bracote Micronic 601EF, Castrol
Braycote? 601 EF is a non-toxic, nonflammable, Perfluorinated Polyether grease that is smooth and buttery in texture and off-white in color. Braycote? 601 EF has an NLGI grade of 2. Castrol Braycote? 601 EF was designed to operate in the presence of rocket fuels, oxidizers, and high vacuum. Additional applications include high load-carrying capabilities, hostile chemical or extreme environmental conditions. Additional benefits of this grease include increased shelf life, high chemical resistance, and extremely low volatility. Braycote? 601 EF has an operating temperature range of -80°C to 204°C.
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Polyrex EM, Exxon Mobil
Polyrex EM is a mineral Polyurea grease that is blue in color smooth and tacky in texture. Polyrex EM is a channeling grease with an NLGI grade of 2. This grease is designed for use in electric-motor bearings where heavy loads and minimum migration are desired. It is considered a replacement for Andoc C lubricant in many industrial applications. Polyrex EM has an operating temperature range of -20 to 350C.
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Nig Ace WS, Nippon Grease Co.
Nig Ace WS is a Diurea synthetic Hydrocarbon grease that is smooth and semi-solid in texture and light brown in color. Nig Ace WS is a channeling grease with an NLGI grade of 2. Nig Ace WS is the lead-reduced, RoHS complaint version of Nig Ace W grease. This grease is commonly used in stepper motor applications as well as encoders and motors where low noise and torque are factors. The operating temperature range of Nig Ace WS is -20 to 150C.
