Four-point contact ball bearings

Four-point contact ball bearings, also called "duplex bearings", belong to the single row angular contact ball bearings family, with split inner ring.
Four-point contact ball bearings are single-row angular contact radial bearings with raceways designed to carry axial loads in both directions. These bearings can support axial loads in both directions including limited radial loads.
Bearings of this type occupy very little axial space compared with double-row bearings. Four-point contact bearings of "QJ" design have a contact angle of 35 °C and are mainly designed to carry axial loads.



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The inner ring is decomposable into two halves. This allows a large number of balls to be inserted into the bearing so as to ensure a high bearing load capacity.
These bearings are decomposable, that is, the inner ring can be mounted separately from the two halves of the inner ring. Both halves of the inner ring of four-point contact bearings have a shoulder with recess. This feature makes oil flow better when the bearing is used in combination with a cylindrical roller bearing.
The presence of these indentations is exploited to facilitate disassembly.

Four-point contact ball bearings are used to carry only thrust loads.

Large housing seats can be used to avoid unwanted radial loads on the bearing.

To prevent the outer ring from rotating in the circumferential direction, these bearings are equipped with locating slots and, for this reason, consist of outer diameters of more than 160 mm. They are manufactured with two locating slots in their outer ring and are positioned 180° apart, identified with the suffix N2.

The special series of four-point contact bearings is available upon request and is represented by the Q10 series, while bearings (four-point contact ball bearings) with a split inner ring are identified by the Q series.

Four-point contact ball bearings are less likely to operate with misalignment, consequently the ability to compensate for any misalignment and tolerance with respect to shaft deflections are also limited. This factor depends on certain factors including internal clearance during operation, bearing size, and the magnitude of forces and moments acting on the bearing.

Misalignments always result in increased noise and stresses on the cage, as well as reduced bearing life.

If bearings of this type are mounted in combination with other radial bearings for use as axial bearings, with low interference fit in the housing, no misalignment of the outer ring with respect to the inner ring is possible.

Four point contact ball bearings are produced to normal tolerance class (PN) as standard.

On request, these bearings are also produced to closer tolerances, such as tolerance classes P6 and P5.

Four-point contact ball bearings have normal axial clearance as standard. Bearings with increased or decreased internal clearance or with restricted clearance limits can be supplied on request.

Four-point contact bearings are, in addition, produced with “enlargements” (axial clearance groups C3 and C4) and/or with reduced axial clearance (C2) upon request.

To ensure satisfactory operation, four-point contact ball bearings (like all ball and roller bearings) must always be subjected to a certain minimum load, particularly if they operate at high speeds or are subject to high acceleration or rapid changes in load direction.

In this case, the inertia forces of the balls and cage, as well as friction in the lubricant, can adversely affect the rolling conditions inside the bearing and can cause harmful creep between the balls and raceways.

External forces exceed the minimum necessary load. Otherwise, the bearing must be subjected to an additional axial load, such as by using springs.

Four-point contact bearings, unless otherwise specified, have solid brass cages as standard.

Other cage types are supplied on request, such as machined solid steel cages, identified by the suffix FPA, and molded polyamide cages, identified by the suffix TVP.

Bearing outer rings arranged as axial bearings with radial clearance in the housing must not be locked, otherwise the outer ring cannot compensate for thermal variations and additional force is generated in the bearing.

When locking of the outer ring cannot be avoided, it must be centered very carefully and precisely during assembly.

  • A = bearings with contact angle of 30°
  • B/BE =bearings with contact angle of 40°, they can withstand high axial loads
  • C = bearings with contact angle of 15°, they can be used in spindles
  • E = bearings with contact angle of 25°, they can be used in spindles
  • CA = axial internal clearance smaller
  • CB = standard internal clearance – standard bearings (C = internal clearance/B = entities of the internal clearance)
  • CC = bigger axial internal clearance (CA – CB – CC they can be mounted next to each other with any arrangement)
  • GA = light preload
  • GB = medium preload
  • GC = heavy preload
  • PN = normal tolerance class
  • J = pressed steel cage
  • TVP = moulded polyamide cage – it can be used at temperatures up to +120°C
  • MP = machined solid brass cages
  • TPA = Phenolic cages – used for high accuracies
  • FP = solid steel cages – used for specific applications
  • ZZ = bearings with shields
  • 2RSR = bearings with seals
  • QJ = four-point contact ball bearings at 35°
  • Q = bearings with split outer ring
  • Q10special series of bearings
  • MPA = standard solid brass cages for four-point contact ball bearings
  • N2 = bearing with two locating slots on the outer ring

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