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| Berliss Bearing Company Home |
| Engineering Data |
LOAD RATINGS-The accompanying tables list the significant dimensions for each size as well as a load rating at 100 RPM. Consult the table below to determine the ratings at other speeds. While load ratings may be a guide in selecting a particular size bearing, experience, available space, and the benefit of a greater safety factor frequently suggests the use of a larger bearing for a particular application. The basic load rating of BERLISS ROLLER BEARINGS assumes an average useful life expectancy of 3000 hours under normal operating conditions. Rarely do these bearings fail from predictable, true fatigue as in the case of other anti-friction bearings. Consequently, the user must consider means to control wear, shock, deflection, misalignment, exclude dirt or any other detrimental material and to provide proper lubrication.
HARDNESS FACTOR-Load ratings for roller assemblies are based on the assumption that shaft and housing have been ground and hardened to Rockwell 58 C or higher. Case hardening is permissible if depth of case is sufficient for the application. If bearings are used on a shaft or housing that has not been hardened to 58 R.C., reduce the load rating by applying the appropriate factor:
| 58 RC=1.00 | 54 RC=0.89 | 50 RC=0.63 | 40 RC=0.22 |
| 56 RC=0.96 | 52 RC=0.78 | 45 RC=0.36 |
ROTATION FACTOR-Ratings are based on conditions where the shaft rotates within a stationary housing. The unit stress concentration is greater when a shaft is stationary in relation to the direction of rotation, consequently the rating must be reduced by 20 percent when this condition exists.
Straight cylindrical roller bearings are produced at three levels of precision depending upon usage. The most economical type is the N A version which uses rollers that are unhardened and unground. the N A H type contains rollers that are case hardened and unground. The highest quality utilizes centerless ground, through hardened alloy steel rollers. Add suffix N A or N A H to the part number to identify classification. Hardened and ground bearings have no suffix.
SELECTION FACTORS-Load ratings are given for through
hardened and ground roller assemblies. Select the appropriate
reduction factor to apply for the particular combination of rollers
and/or split outer race. Case hardened, unground rollers as well
as unhardened, unground rollers do not have the characteristics
of fatigue that prevails in other anti-friction bearings. Therefore,
according to the AFBMA, no rating may be used with these products.
Listed below are modifying service factors that have proven to
be rather accurate during the many years of their general usage:
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| Roller assemblies with Hardened and Ground rollers | 1.00 | |
| Roller assemblies with NAH rollers | 0.50 | |
| Roller assemblies with NA rollers | 0.20 | |
| Complete bearings with H & G rollers with HP or HPA race | 0.50 | *** |
| Complete bearings with H & G rollers with P or PA race | 0.30 | |
| Complete bearings with NAH rollers with HP or HPA race | 0.38 | *** |
| Complete bearings with NA rollers with any race | 0.20 | |
| Complete bearings with NAH rollers with P or PA race | 0.25 | |
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| SPEED FACTORS - | |||
| RPM | FACTOR | RPM | FACTOR |
| 0-10 | 2.000 | 200 | .812 |
| 25 | 1.516 | 300 | .719 |
| 50 | 1.230 | 500 | .617 |
| 75 | 1.090 | 750 | .547 |
| 100 | 1.000 | 1000 | .501 |
LIMITING SPEED-Suitable lubrication must be available for high speed applications to remove excess heat and to minimize internal friction. 1200 feet per minute surface speed of the shaft should be considered the maximum allowable speed.
LUBRICATION-While oil may be the best lubricant, grease is generally used with our bearings for the convenience of retention. Washer seals shown on page 20 offer a simple means of bearing and lubricant retention as well as the exclusion of foreign matter.
| SHAFT AND HOUSING TOLERANCES FOR ASSEMBLIES AND SPLIT RACE BEARINGS | ||||||
| BEARING CLASSIFICATION |
NOMINAL
BEARING BORE* |
NOMINAL BEARING O.D.* |
SHAFT TOLERANCES |
HOUSING TOLERANCES** |
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| Roller Assembly only
(hardened and ground) | 3/8" - 4" 3/8" - 4" | 3/4" - 2" 2 1/16 - 4' | +.0000" +.0000" | -.0010" -.0010" | +.0010" +.0010" | +.002" +.0025" |
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| Roller Assembly with split outer race (hardened and ground) | 3/8" - 4" 3/8" - 4" | 3/4" - 3" 3 1/16" - 6" | +.0000" +.0000" | -.0010" -.0010" | +.001" +.002" | +.005" +.007" |
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| Roller Assembly only
(NA and NAH series) | 3/8" - 1 " 1 1/16" - 2" 2 1/16" - 4" | 3/4" - 3" 3 1/16" - 6" | +.000" +.000" +.000" | -.002" -.003" -.004" | +.001" +.002" | +.005" +.007" |
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| Roller Assembly with split outer race (NA and NAH series) | 3/8" - 1 " 1 1/16" - 2" 2 1/16" - 4" | 3/4" - 3" 3 1/16" - 6" | +.000" +.000" +.000" | -.002" -.003" -.004" | +.001" +.002" | +.005" +.007" |
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NOTE: * All dimensions listed are inclusive, e.g., from 3/8 to and including 4". ** e.g., Housing Bore for 1.250 nominal equals 1.251 - 1.252. *** HP and HPA Races are hardened. | ||||||