In order to improve the bearing capacity and rigidity of precision bearings, angular contact ball bearings for machine tool spindles are usually used in combination with two or more sets of bearings.
1. Universal matching bearing
Universal pairing, that is, the same group of universal pairing bearings can be paired arbitrarily in the form of back-to-back, face-to-face, and tandem. The protrusions at both ends of a single set of universal matching bearings are exactly the same.
The preload load of universal matching bearings is also divided into four types: light preload A, medium preload B, heavy preload C, and special preload.
In addition to meeting the relevant external dimension tolerance and rotation accuracy requirements for a single set of bearings used in paired bearings, there are strict requirements for the following performances between any two sets of bearings in the paired bearings:
A: The average inner diameter of any two sets of bearings is different from each other
B: The radial runout difference between any two sets of bearing inner rings
C: The average outer diameter of any two sets of bearings is different from each other
D: The difference between the radial runout of any two sets of bearing outer rings
E: The actual contact angles of any two sets of bearings are different from each other
F: The protrusion of two adjacent sets of bearings is different from each other
1. Two pairs of paired bearings are available in three forms: back-to-back (DB), face-to-face (DF) and tandem (DT).
Features of pairing of bearings
Pairing form Code Features
Back-to-back DB symmetrical installation
Capable of bearing radial loads
Capable of bearing axial loads in 2 directions
Capable of withstanding high overturning moments
Face-to-face DF symmetrical installation
Capable of bearing radial loads
Capable of bearing axial loads in both directions
Able to slightly adjust the center, poor ability to withstand overturning moment
Tandem DT Both sets of bearings are identical
alignment
Capable of bearing radial loads
Capable of bearing large axial loads in one direction

2. Multiple pairs
In order to achieve higher load capacity and rigidity, angular contact ball bearings for machine tool spindles can also be matched in triple, quadruple, or quintuple pairs.
For paired bearings, the bearing direction is different, and the working performance of the paired bearings is also different. Therefore, paired bearings, especially asymmetrically arranged paired bearings, have a certain installation direction. For this reason, an angular line is marked on the outer ring of its matching bearing along the axial direction: “∨”, the opening of the angular line “∨” faces the axial load acting on the inner ring, that is, the direction of the sharp angle of the angular line “∨” It should be consistent with the direction of the axial load on the inner ring of the bearing only. If the load acting on the inner ring of the bearing is bidirectional, that is, the direction of the sharp corner of the angle line “∨” should be consistent with the direction of the larger axial load acting on the inner ring of the bearing.