NTN - Cylindrical and Tapered Roller Bearings

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Engineering Section Glossary of Symbols A a 1 a 2 a 3 a 4 a 5 B C Cr Cor CCW CF CW D E e F F a F n F r Cylindrical bearing inner ring raceway diameter Life adjustment factor for reliability Life adjustment factor for material Life adjustment factor for lubrication Life adjustment factor for misalignment Life adjustment factor for load zone size Bearing inner ring bore Cylindrical bearing outer ring raceway diameter Bearing dynamic load rating (ISO) Bearing static load rating (ISO) Counterclockwise Centrifugal force Clockwise Bearing outside diameter Modulus of elasticity Equivalent load factor Force Thrust (Axial) component of F n or axial force Normal force Radial force L’ n Adjusted bearing life @ n reliability level LH MPD N n n P P PD p Q R n RH r S T 1 T 2 TR n W Wt Y 1 Left hand Mean pitch diameter Number of teeth in gear “n” Subscript index Equivalent radial load for tapered roller bearings Subscript for pinion Pitch diameter Radial contact pressure Torque Bearing “n” radial reaction Right hand Radius Rotational speed (rpm) Belt tension-tight side Belt tension-loose side Thrust reaction of tapered bearing “n” Gear face width Weight Axial load factor F s Separating component of F n Y 2 Axial load factor F t f pl G H HP IF J K L 10 L n Tangentail component of F n Preload factor Subscript for ring gear Housing O.D. Horsepower Interference fit Hollow shaft I.D. Ratio of radial to thrust rating for tapered roller bearings Bearing life @ 90% reliability level Bearing life @ n reliability level L’ 10 Adjusted bearing life @ 90% reliability level (alpha) (beta) (beta) i (delta) o (delta) (nu) 1/2 included cup angle Pitch angle for straight, zerol, and spiral bevel gears Face angle of hypoid pinion and root angle of hypoid gear Change in inner ring raceway diameter Change in outer ring raceway diameter Poisson’s ratio (sigma) Summation (phi) r (phi) (psi) Normal pressure angle Pressure angle in plane of rotation Helix or spiral angle 3
Roller Bearings INTRODUCTION The selection of the proper bearings for all mechanical systems is essential to the functional and commercial success of that system. The bearings must not only be of the right type, but also the correct size to assure reliability and cost effectiveness. The bearings must be installed properly, supplied with the correct lubricant, and provided with a compatible environment for the system to be successful. This catalog is designed to provide guidelines for the engineer to follow in making proper bearing selection and in establishing an operating environment that will lead to reliable system performance. Because it is impossible to cover all aspects of bearing selection within any text due to the vast number of variables encountered, NTN maintains a staff of Bearing Application Engineers to assist customers in making bearing selections for applications of all kinds. We urge our customers to take advantage of this service. Application engineering assistance may be obtained by calling NTN Sales, or by contacting: NTN Bearing Corporation of America Application Engineering Department 1600 E. Bishop Court Mt. Prospect, IL 60056 847-298-7500 (Fax: 847-294-1208) BEARING LIFE DEFINITION All roller bearings have finite lives. Therefore, it is necessary to develop techniques to estimate their lives. Theoretical bearing life is defined as the time (measured in revolutions) to the initial occurrence of rolling contact fatigue on either raceway or any rolling element. Rolling contact fatigue is subsurface initiated damage that occurs after many revolutions of the bearing. When a bearing is rotated under load, the raceways and rolling elements are subjected to cyclic Hertzian stresses as they pass through the load zone. After millions of cycles, microscopic cracks form beneath the bearing surfaces. As the bearing continues to operate, the cracks eventually propagate to the surface causing small particles of steel to break away from the surface. This type of damage is called spalling. See Figure 1. The laboratory criterion used to define the fatigue FIGURE 1 life of a bearing is the time period until either raceway or any rolling element develops a spall with an area of 0.01 in 2 (6 mm 2 ). This definition is necessary for a meaningful comparison of bearing lives under controlled conditions. However, in many applications, a spall of this size may have no immediate or short term adverse effect on total system performance. The size of a spall before a bearing becomes unsuitable for further use is dependent on the nature of the application and how much noise, vibration, or both can be tolerated. The time when a bearing becomes unsuitable for further service is sometimes referred to as its useful life in contrast to its fatigue life. The length of the period between the fatigue life and the useful life is a function of the stress level, the steel alloy and its heat-treatment, and the lubrication. Further information on this subject may be obtained from the NTN Application Engineering Department. It is impossible to predict the exact fatigue life of an individual bearing. A group of apparently identical bearings subjected to the same conditions of load, speed, lubrication, and temperature will produce a considerable scatter of fatigue lives. Therefore, statistical methods are required to predict the life of the group. The Weibull distribution is generally used to evaluate these types of data. It is common practice to specify the life of the group at the L 10 level which is the life that 90% of the group will achieve or exceed. Stating this another way, 10% of the group will have experienced fatigue of one or more components at the L 10 level. Many other factors besides fatigue may effect bearing performance. These include lubrication, misalignment, contamination, internal operating clearance, etc. Evaluation of these parameters is addressed in the life adjustment factor portion of the Bearing Life Calculations section, page 14. 4
Page 1 and 2: CylindriCal and Tapered roller Bear
Page 4 and 5: Table of Contents INTRODUCTION. . .
Page 6 and 7: Table of Contents TAPERED ROLLER BE
Page 8 and 9: Introduction Cylindrical Roller Bea
Page 12 and 13: Engineering Section BEARING LOAD RA
Page 14 and 15: Engineering Section Tangential Comp
Page 16 and 17: Engineering Section An Imbalance Fo
Page 18 and 19: Engineering Section SPECIAL CASES V
Page 20 and 21: Engineering Section The These value
Page 22 and 23: Engineering Section lubrication the
Page 24 and 25: Engineering Section a 3 —Lubricat
Page 26 and 27: Engineering Section LIMITING SPEEDS
Page 28 and 29: Engineering Section LUBRICATION The
Page 30 and 31: Engineering Section Grease GREASE G
Page 32 and 33: Introduction Cylindrical Roller Bea
Page 34 and 35: Introduction Bearing CAGES “M”
Page 36 and 37: Bearing Selection STANDARD SERIES M
Page 38 and 39: Bearing Selection Bearing Types SEP
Page 40 and 41: Bearing Selection Bearing Types SEP
Page 42 and 43: Bearing Selection Bearing Types NON
Page 44 and 45: Dimensions and Ratings r Wr r r R R
Page 46 and 47: Dimensions and Ratings r r H A C F
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Dimensions and Ratings r r H A C F
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Dimensions and Ratings W MAX-PAK (M
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Dimensions and Ratings C W MOJ & MO
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Dimensions and Ratings Custom “R
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Dimensions and Ratings “R” Seri
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Dimensions and Ratings Mast and Cha
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Dimensions and Ratings Rotational o
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Dimensions and Ratings Outer Ring G
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Dimensions and Ratings Internal Dia
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Dimensions and Ratings Internal Dia
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Mounting and Fitting Practice Gener
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Mounting and Fitting Practice Inner
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Mounting and Fitting Practice Inner
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Mounting and Fitting Practice 1900
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Mounting and Fitting Practice Outer
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Mounting and Fitting Practice Shaft
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Mounting and Fitting Practice Housi
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Introduction Tapered Roller Bearing
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Introduction Bearing Design True Ro
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Bearing Selection by Bore Size Bear
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Bearing Selection by Bore Size Bear
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Dimensions and Ratings W W W o W o
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Dimensions and Ratings Load Rating:
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Dimensions and Ratings T W f D f W
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Dimensions and Ratings W p W p W i
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Dimensions and Ratings Bore Diamete
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Tolerances Tolerances for Metric Sy
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Fitting Practice Tables Cone Fittin
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NTN - Cylindrical and Tapered Roller Bearings

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