Smooth SelfAligning Ball Bearings
Self-aligning ball bearings are available in two main types
1. Basic design bearings
2. Bearings with rubber seals on both sides
Basic Design
The basic design bearings are available with either cylindrical bore or tapered bore (taper ratio 1:12). Self-aligning ball bearings with a tapered bore can be directly mounted on tapered shaft diameters using a locking nut. Alternatively, they can be easily installed on cylindrical shafts using appropriate adapter sleeves or withdrawal sleeves. The radial clearance of the bearing can also be adjusted using an adapter sleeve.
The internal design of the basic self-aligning ball bearings has been improved, providing higher load-carrying capacity compared to the original standard design. As a result, these bearings offer broader applicability—either enabling the same-sized bearing to carry heavier loads or, under unchanged load conditions, improving operational reliability and extending service life.
Sealed Bearings
Self-aligning ball bearings can be equipped with contact seals on both sides, such as 2RS or 2RS1 type seals. These seals are made of wear-resistant synthetic rubber reinforced with thin steel plates. The bearings are permanently lubricated and require no maintenance. They should not be heated or cleaned before installation.
Dimensions
The basic dimensions of self-aligning ball bearings comply with ISO 15:1981 and are listed in the dimension tables.
Angular Misalignment
Self-aligning ball bearings are designed to accommodate angular misalignment between the inner and outer rings.
The maximum allowable angular misalignment under normal operating conditions is provided in the table below. Whether the maximum value can be utilized depends on the bearing configuration design and the type of seals used.
Tolerances
Self-aligning ball bearings are manufactured with standard (normal) tolerance grades. Precision grades such as P6 and P5 are also available. Tolerance grades can be referenced in the corresponding tables.
Radial Internal Clearance
Standard self-aligning ball bearings are supplied with normal radial internal clearance. Bearings with a tapered bore are supplied with C3 group clearance as standard. Bearings with internal clearance greater or smaller than the standard value can be produced according to customer requirements. Radial clearance values can be found in the clearance tables.
Cages
The standard cage for self-aligning ball bearings is made of glass fiber-reinforced nylon 66. This material offers advantages such as good processability, light weight, and self-lubricating properties. It can accommodate higher operating speeds and withstand temperatures up to +120°C.
For bearings operating continuously under high temperatures or harsh conditions, stamped steel cages or machined brass cages are available. For non-standard cage requirements, please contact the technical department.
Minimum Load
To ensure satisfactory operation of ball and roller bearings, a certain minimum load must be applied. This requirement also applies to self-aligning ball bearings. Otherwise, at high speeds, inertial forces acting on the balls and cage, along with friction from the lubricant, may adversely affect rolling behavior, causing destructive sliding between the balls and raceways.
The minimum required load can be estimated using the following formula:
F_{rm} = k_r \cdot \left( \frac{\gamma \cdot n}{1000} \right)^{2/3} \cdot d_m^{3.3}
Where:
· F_{rm}: Minimum radial load (N)
· k_r: Minimum load coefficient
· = 40 for series 12 and 13 bearings
· = 45 for series 22 bearings
· = 50 for series 23 bearings
· \gamma: Operating viscosity of the lubricant at operating temperature (mm²/s)
· n: Rotational speed (r/min)
· d_m: Bearing mean diameter = 0.5(d + D) (mm)
The weight of the supported components plus external forces often exceeds the minimum load. If not, additional loads must be applied, such as increasing belt tension or using other similar methods.
Dynamic Equivalent Bearing Load
· P = F_r + Y_1 \cdot F_a (kN) when \frac{F_a}{F_r} \leq e
· P = 0.65F_r + Y_2 \cdot F_a (kN) when \frac{F_a}{F_r} > e
Values for Y_1, Y_2, and e are listed in the bearing dimension tables.
Static Equivalent Bearing Load
P = F_r + Y_0 \cdot F_a \quad \text{(kN)}
The value of Y_0 is provided in the bearing dimension tables."