Machinery's Handbook, 31st Edition
2404
Bearing Lubricants
Boundary and Mixed-Film Lubrication Heavy Load Light Load
Grease
SAE 10 SAE 20 SAE 30 SAE 40 SAE 50
Full-Film Lubrication Heavy Load 250 psi Light Load 100 psi
SAE 5
10
20
40 60 100 200 400 600 1000 2000 4000 6000 10,000
Journal Speed, N (rpm)
Fig. 7. Lubricant Selection Guide Table 1. Commonly Used Greases and Solid Lubricants
Operating Temperature
Type
Load
Comments
° F
° C Greases
Calcium or lime soap
160 300 180 300 350
71
Moderate
…
Sodium soap Aluminum soap Lithium soap Barium soap
149 82 149 177
Wide
For wide speed range
Moderate
…
Moderate Good low temperature
Wide
…
Solid Lubricants
Graphite
1000
538
Wide Wide
…
Molybdenum disulfide − 100 to 750 … Synthetic greases are composed of normal types of soaps but use synthetic hydrocarbons instead of normal mineral oils. They are available in a range of consistencies in both water-soluble and insoluble types. Synthetic greases can accommodate a wide range of variation in operating temperature; however, recommendations on special-purpose greases should be obtained from the lubricant manufacturer. –73 to 399 Application of grease is accomplished by one of several techniques depending upon grease consistency. These classifications are shown in Table 2 along with typical methods of application. Grooves for grease are generally greater in width, up to 1.5 times, than for oil. Coefficients of friction for grease-lubricated bearings range from 0.08 to 0.16, depend ing upon consistency of the grease, frequency of lubrication, and type of grease. An aver age value of 0.12 may be used for design purposes. Solid Lubricants: The need for effective high-temperature lubricants led to the develop ment of several solid lubricants. Essentially, solid lubricants may be described as low- shear-strength solid materials. Their function within a bronze bearing is to act as an intermediary material between sliding surfaces. Since these solids have very low shear
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