Self-aligning Ball Bearings

Self-aligning ball bearings have a common sphered raceway in the outer ring. This feature allows angular misalignment of the shaft relative to the housing. Therefore self-aligning ball bearings are particularly used in case of bearings where misalignment can occur from errors in mounting or from shaft bending. Double row self-aligning ball bearings are manufactured both with cylindrical bore and tapered bore (taper 1:12). Self-aligning bearings with tapered bore can be delivered, at request, with adapter sleeves.

Sealed self-aligning ball bearings

Self-aligning ball bearings are also available in a sealed version with seals at both sides. The seals are made of gasoline, oil and wear-resistant synthetic rubber. Sealed bearings are delivered filled with a certain grease quantity. Sealed bearing operating temperatures are between -30?C and +80?C. Grease service life is much reduced if bearing operates at a temperature higher than + 80?C (see Chapter 5). Sealed bearings are greased for the entire operating period, relubrication not being necessary. Sealed bearings washing or heating before mounting in assembly is not allowed.

Self-aligning ball bearings with extended inner ring

Self-aligning ball bearings with extended inner ring of series 112 and 113 are used in applications where high accuracy is not necessary and generally, they can be mounted directly on rolled shafts. The bore manufactured to tolerance class J7 allows fast mounting and dismounting. The innerring has a groove for bearing axial location which can be done by means of a screw or pin.

Dimensions

Overall dimensions of self-aligning ball bearings are in accordance with ISO 15.

Misalignment

Self-aligning ball bearings allow within certain limits an angular misalignment of the outer ring in relation to the inner ring, without detrimental effects in bearing unit. Approximate values for permissible misalignment, under normal operating conditions are given in table 1.

Tolerances and radial clearance

Bearings of serial production are manufactured to normal tolerance class and with normal radial clearance. Tapered bore bearings of serial production are also manufactured with radial clearance C3. Self-aligning ball bearings with extended inner ring are manufactured with radial clearance C2 and normal clearance. At request, these bearings can also be manufactured to other tolerance classes and with smaller or larger radial clearance. The bore of self-aligning ball bearings with extended inner ring is manufactured to tolerance class J7. Bearing tolerances are given on page 24 and the values of radial clearance are given in tables 2 and 3.

Equivalent dynamic radial load

Pr = Fr + Y1Fa, kN, when Fa/Fr e The values of factors e, Y1 and Y2 which depend on bearings are given in bearing tables.

Equivalent static radial load

P0r = Fr + Y0Fa, kN The values of the factor Y0 which depends on bearing are given in bearing tables.

Axial load on bearings with adapter sleeve

If self-aligning ball bearings are mounted with adapter sleeves on smooth shafts, without side location, their axial carrying capacity depends on the friction between the sleeve bore and shaft. Permissible axial load can be precisely enough determined using the equation:

Fa max = 3 B d

where:

Fa max – maximum permissible axial load, N

B – bearing width, mm

d – bearing bore diameter, mm

Cages

Self-aligning ball bearings are generally fitted with pressed cages of sheet. At special request, when bearings operate under fluctuating loads, at high speeds and where large sizes are required, machined brass cages are recommended to be used. Glass fibre reinforced polyamide 6.6 cages are also suitable if the operating temperatures do not exceed +12CTC. They have low weight, a low coefficient of friction and are noiseless while running. Cage design and technical data are given in table 4.