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Precision Spindle Bearings

Precision Spindle Bearings

Characteristics of spindle bearings
Spindle bearings are single row angular contact ball bearings comprising solid inner and outer rings and ball and cage assemblies with solid window cages. They cannot be dismantled. The bearings are available in both open and sealed versions.
Spindle bearings have restricted tolerances. They are particularly suitable for where requires very high guidance accuracy and speed capacity, especially for slewing part of the main spindle of machine tool.
Angular contact ball bearings have raceways in the inner and outer rings that are displaced with respect to each other in the direction of the bearing axis. This means that they are designed to accommodate combined loads, i.e. simultaneous radial and axial acting loads.
The axial load carrying capacity of angular contact ball bearings increases with the enlarging of contact angle. The contact angle α is defined as the angle between the line joining contact point of the ball and the raceways in the radial plane, along which the load is transmitted from one raceway to another, and a line perpendicular to the bearing axis.
Single row angular contact ball bearings can accommodate axial loads acting in one direction only. Under radial loads a force acting in the axial direction is engendered in the bearing, and this force must be counteracted. Consequently the bearing is normally adjusted via a second bearing.
Single row angular contact ball bearings have one high and one low shoulder. Some bearings, particularly those of Diameter Series 8 and 9, have an inner ring with two high shoulders as a deep groove ball bearing. The low shoulder on one or both rings enables a large number of balls to be filled in the bearing, thus giving the bearings a relatively high load carrying capacity. They are of inseparable design.
The contact angle αis 15°(C) or 25°(E), designation suffix C.T.P4S or E.T.P4S.F, for the most common sizes, the cage is a solid window type cage made of textile-laminated phenolic resin(T) and the tolerance class is P4S. Single row angular contact ball bearings are produced in two versions.
Bearings for universal matching
basic design bearings(not universally matchable) can be only be used for arrangements with single bearings
Bearing Tolerances
Bearing "tolerances" of dimensional and running accuracy, are regulated as ISO standard. For dimensional accuracy, these standards prescribe the necessary tolerances when installing bearings on shafts or in housings, consisting of the acceptable values for bore diameter, outer diameter, assembled bearing width, the permit chamfer, and tapered bore deviation. The geometry accuracy includs average bore diameter variation, outer diameter variation, average outer diameter parattelism, as well as raceway width and height variation(for thrust bearings).
Running accuracy is defined as the allowable limits for bearing runout during operation, consisting of the acceptable values for inner and outer ring radial and axial runout, inner ring side runout, and outer diameter perpendicular deviation.
Comparison of tolerance classifications of national standards


Tolerance Class Bearing Types
Chinese Industrial Standard(GB) GB 307.1 P0 P6 P5 P4 P2 All types

for Standardization(ISO)

ISO 492 Class 6x Class 6 Class 5 Class 4   Radial bearings
ISO 199 Normal class Class 6 Class 5 Class 4   Thrust ball bearings
ISO 1224     Class 5A Class 4A   Precision instrument bearings
Deutsches institut for Normung(DIN) DIN 620 P0 P6 P5 P4 P2 All types
Criteria for selecting bearing internal clearance
A bearing's life is theoretically maximum when operating clearance is slighly negative at steady operation. In reality it however is difficult to constantly maintain this optimal condition.If the negative clearance becomes enlarged by fluctuant operating conditions, heat will be produced and bearing life will decrease dramatically. Under ordinary circumstances you should therefore select an initial internal clearance where the operating clearance is slightly larger than zero.
For ordinary operating conditions that use fitting for ordinary loads, running speed and operating temperature are ordinary,selecting normal clearance enables you to obtain the proper operating clearance.
Radial internal clearance for duplex angular contact ball bearings
Nominal bore Diameter C2 CN C3 C4 C5
d mm
over incl.
min max min max min max min max min max
10 18 3 8 6 12 8 15 15 24 30 40
18 30 3 10 6 12 10 20 20 32 40 55
30 50 3 10 8 14 14 25 25 40 55 75
50 80 3 11 11 17 17 32 32 50 75 95
80 100 3 13 13 22 22 40 40 60 95 120
100 120 3 15 15 30 30 50 50 75 110 140
120 150 30 16 16 35 35 55 55 80 130 170
150 180 3 18 18 35 35 60 60 90 150 200
180 200 3 20 20 40 40 65 65 100 180 240
Note:The Clearance group in the table is applied only to contact angles in the table below
Contact angle Nomial Contact Applicable clearance group
Symbol angle          
C 15° C1 C2      
A 30°   C2 CN C3  
B 40°     CN C3 C4
Designation bearing sets
Bearing sets consist of bearings with matched bore and outside diameters. The first letter refers to the number of bearings in a set.
D 2 bearings Duplex
T 3 bearings Triplex
Q 4 bearings Quadroplex
Ready-to-mount bearing sets feature a defined order of bearings. The second (and sometimes third) letter refers to the arrangement of the bearings within the set:
B back-to-back arrangement
F face-to-face arrangement
T tandern arrangement