Precision Rolling Bearings
78Pages

Technical Description Technical Description Bearing Selection Bearing Life Bearing Tolerance Bearing Arrangement Preload and Rigidity Lubrication Limiting Speeds Shaft and Housing Design Bearing Handling

Bearing Selection 1 -1 Bearing Selection Procedure '.V iik; i! i:- m: to 'i: thn cpt nu n taring tysc a'd corana™. :hí eos oner shou : -D-=i(i.-r n v ng priority to meeting the most critic it is no exaggeration lo say thai bearing selection is essential inorderlo requirement ot the bearing. Figure 1 -ï provides an example ola obtain the desired design performance and service life. procedure based on the estao shren p'ioltii -"or ts 'rqu id lit While there is no "best" procedure tor selecting the optimal bearing, characteristics. • Figure 1.1 Bearing Selection Procedure

NACHI BEARING Technical Description 1-2 Examine Bearing Type Factors Selection guidelines Allowable space for bearings ● When designing a shaft system, the rigidity and strength of the shaft are important factors. The rst step is to determine the shaft diameter, and the bore diameter. ● Figure 1.2 shows guidelines for the main precision rolling contact bearings types and sizes used in machine tools. Load (type, direction, magnitude) ● Select the optimum bearing type in accordance with the magnitude of radial and axial load, direction of the load (either one or both directions), and level...

Technical Description 2 Bearing Life 2-1 Basic Dynamic Load Rating and Rated Life Although the requirements of rolling contact bearings vary somewhat with the individual application, the principal requirements are: ● High load capabilities ● Low friction ● Smooth and quiet rotation ● High accuracy ● High rigidity The reliability or durability requirement sets the time frame over which all other requirements are to be maintained. The reliability requirement (life in the broad sense) includes grease and acoustic life, as well as fatigue life. Reliability is reduced by various type of damage...

NACHI BEARING Technical Description 2-3 Angular Contact Ball Bearing Load In the case of angular contact ball bearings, the points where the extended contact lines within the bearing and the axis as shown in Figure 2.1 must be used as the bearing support points (load centers). Because of this, angular contact ball bearings are shown in dimension tables with "a" dimensions indicating support point positions. This consideration is particularly important when a moment load is acting on a bearing series. Axial component forces are generated when a radial load acts on an angular contact ball...

Technical Description Bearing Life 2-4 Basic Static Load Rating and Static Equivalent Load ● Table 2.3 Static Load Factors 2.4.1 Basic Static Load Rating Load applied to stationary bearings can create permanent indentions in the load surfaces. While some level of deformation can be tolerated, a level of deformation will be reached where noise and vibration during operation of the bearing, will make the bearing unusable. The term Basic Static Load Rating (Cor or Coa) refers to the maximum contact stress value of the static load when the rolling element and raceways contact. Ball bearings —...

NACHI BEARING Technical Description 3-2 Tolerances and Permissible Values of Angular Contact Ball Bearings for Thrust Loads (TAH/TBH Series) Except for the outside diameter of outer ring outside diameter, accuracy of angular contact ball bearings for thrust loads conforms to JIS Class 4. Outside diameter of outer ring tolerances is as shown in Table 3.3. ● Table 3.3 Tolerance of Outside Diameter Nominal bearing outside diameter D (mm) Unit: μm Outside diameter deviation Ds Over Incl. High Low 50 80 120 180 250 80 120 180 250 315 -30 -36 -43 -50 -56 -49 -58 -68 -79 -88 Bearing Selection...

Technical Description Bearing Tolerence 3-4 Ball Screw Support Bearing (TAB Series) Tolerances Tolerances for ball screw support (TAB Series) is shown in Table 3.6 and Table 3.7. ● Table 3.6 Tolerances for Inner Ring (Including Outer Ring Width and Outer Ring Sideface Runout Reference to Raceway) Nominal bearing bore diameter d (mm) Single plane mean bore and bore variation d mp, d s Class 5 Class 4 Bore diameter variation in a single radial plane Mean bore diameter variation Vd mp Vd p Deviation of a single inner ring width (or a single outer ring width) B s, C s Unit: μm Side face runout...

NACHI BEARING Technical Description 3-5 Tolerances for Ball Screw Support Bearing (TAF Series) Tolerances for ball screw support (TAF Series) is shown in Table 3.10 and Table 3.11. ● Table 3.10 Tolerances for Inner Ring (Including Outer Ring Width, JIS Class 5) Nominal bearing bore diameter d (mm) Bore diameter Mean bore variation in a diameter single radial variation plane Single plane mean bore diameter variation d mp Vd mp Vd p Unit: μm Radial runout Width Outer and inner ring width of assembled deviation VBS variation bearing inner of Inner Ring ring B s, C s VB s K ia Side face Side...

Technical Description 4 Bearing Arrangement 4-1 Duplex Bearing Features In addition to a duplex set, precision angular contact ball bearings and ball screw support bearings are available in 3-row duplex and 4-row duplex. Bearings in these combinations are manufactured in sets with a desired preload and dimensional variation of outside diameter and bore diameter within the bearing sets are controlled. Because of this, avoid switching the duplex bearings in a set with other bearings. Table 4.1 shows the main combinations and describes their characteristics. ● Table 4.1 Main Combinations and...

NACHI BEARING Technical Description 4-2 Mounting and Mounting Symbols The symbols used for each type of combination are shown in Table 4.1. The arrangement sequence and direction of the load are important for duplex bearings. Because of this, the outside surface of the outer ring of the duplex bearings in Figure 4.1 has a combination mark ([<]) that can be used to check the arrangement sequence. If the bearings are arranged in the correct sequence, the marks on the outside surface of each bearing appear as a "<" Bearing Selection DB DF DT FFB BFF FFF Bearing Life Bearing Tolerance Bearing...