Double row angular contact ball bearings
With optimal size of the balls and their conformity to the raceways relatively high load ratings are achieved. They can carry axial and radial loads in both directions
and are suitable even for high rotation rate. In case of “E” type bearings assembling, it must be done so that the prevailing axial force acts on the ball row on the side without the filling groove.
Main dimensions of double row angular contact ball bearings specified in the dimension tables are in accordance with the international standards ISO 15. The bearings are commonly produced in the basic P0 tolerance class. Double row angular contact ball bearings are very sensitive to the misalignment of the rings.
Bearings with shields or seals
Double row angular contact ball bearings with sealing on one or on both sides are manufactured with metal shields (Z, -2Z) or with seals (RS, -2RS). The sealing rings made of rubber, vulcanized on metal reinforcing ring, provide an effective friction type sealing. The bearings are manufactured in the design with a seal and a flat collar of the inner ring (RS, -2RS).
Bearings with seals are suitable for operation within the temperature range from -30°C to 110°C.
Bearing deliveries with sealing capacity within 180°C (RS2, -2RS2), or eventually delivery of bearings with other sealing design, must be negotiated in advance.
Bearings sealed on both sides (-2Z, -2RS) are filled with a quality lubricant the properties of which usually ensure the lubrication during the whole bearing life under normal operating conditions. The bearings of this design cannot be relubricated. They can be used within the operating temperature range from -30°C to 110°C. The delivery of bearings with different lubricant should be discussed with the supplier in advance.
For bearings sealed on both sides, the designation of the lubricant filling different from standard lubricant is indicated by a symbol combination. The first two letters indicate the operating temperature range (a symbol in accordance with STN 02 4608) and the third identifies the lubricant name.
TL – Lubricant for low operating temperatures (from -60°C to 100°C)
TM – Lubricant for medium operating temperatures (from -30°C to 110°C)
TH – Lubricant for high operating temperatures (from -40°C to 250°C)
TW – Lubricant for low and high operating temperatures (from -40°C to 150°C)
Note: The symbols of lubricants for medium operating temperatures need not to be marked on the bearings.
The single row deep groove ball bearings of the basic design are equipped with a pressed cage made of steel sheet, guided on balls, which is not designated. The cages for double row angular contact ball bearings are manufactured in two version in dependence on the inner construction of the bearing. (see picture).
In special cases the bearings are produced with different types of cages: bearings with a solid polyamide cage (TNH, TNGH), with a solid cage of textite (TB). The supply of these bearings should be discussed in advance.
Single row deep groove ball bearings are produced in tolerance classes P0 and P6. For special arrangements requiring high precison or for arrangements with a high rotation speed, the bearings with higher tolerance classes P6, P5 and P4 are used. The bearings with higher tolerance class P6E are used for rotating electric machines. The limit values of deviations in tolerances and the operation are specified in ISO 492.
Normally produced double-row ball bearings with oblique contact have normal axial clearance which is not marked. For special cases, the bearings with reduced axial clearance (C2) or enhanced axial clearance (C3, C4, C5) are supplied.
Commonly produced double row angular contact bearings have standard vibration level specified by the manufacturer. For special arrangements with silent running bearings with reduced vibration level (C6) are produced.
Combination of symbols
The symbols for the tolerance classes, internal bearing clearances and vibration levels are combined with the simultaneous omission of the symbol C in the second and the following bearing special characteristics e. g.:
P6 + C3 = P63
C3 + C6 = C36
P6 + C3 + C6 = P636
The misalignment of the rings is not admissible for double row angular contact ball bearings. The misalignment causes additional load of the bearing and the durability is lowered.
Radial equivalent dynamic load
Double row angular contact ball bearings:
P = Fr + 0,73.Fa
P = 0,67.Fr + 1,41.Fa
for Fa/Fr ≤ 0,68
for Fa/Fr > 0,68
The designation of basic designs and common modifications of the bearings are specified in the dimension tables. Modification of the basic design is designated with additional symbols according to STN 02 4608. The meaning of the most used symbols for single row deep groove ball bearings is in the table.
|Symbol||Example of Designation||Meaning|
|-RS||3205RS||Seal on one side adhering to a flat surface of the inner ring|
|-2RS||3307-2RS||Seal on both sides adhering to a flat surface of the inner ring|
|-Z||3206-Z||Metal shield on one side|
|-2Z||3208-2Z||Metal shields on both sides adhering to a flat surface of the inner ring|
|TNH||3309TNH||Plastic cage guided on balls|
|P6||3205 P6||Higher tolerance class than standard|
|P5||3307E P5||Higher tolerance class than P6|
|C2||3304 C2||Radial clearance less than normal|
|C3||3305-2Z C3||Radial clearance greater than normal|
|C4||3307-2RS C4||Radial clearance greater than C3|
|C5||3206-2Z C5||Radial clearance greater than C4|
|C6||3305 C6||Reduced vibration level|