Double Row Deep Groove Ball Bearings

SKF double row deep groove ball bearings correspond in design to single row deep groove ball bearings. They have deep uninterrupted raceways and high conformity between the balls and raceways. They are able to carry axial loads acting in both directions in addition to radial loads.

Double row deep groove ball bearing

Double row deep groove ball bearings are very suitable for bearing arrangements where the load carrying capacity of a single row bearing is inadequate. For the same outside and bore diameters, double row bearings are slightly wider than single row bearings but have considerably higher load carrying capacity than single row bearings in the 62 and 63 series.

Dimensions The boundary dimensions of SKF double row deep groove bearings are in accordance with ISO 15:1998.

Tolerances SKF double row deep groove ball bearings are produced to Normal tolerances. The values for tolerances correspond to ISO 492:2002.

Internal clearance SKF double row deep groove ball bearings have Normal radial internal clearance as standard. The clearance limits are as specified in ISO 5753:1991.

Misalignment Misalignment of the inner ring relative to the outer ring of a double row deep groove ball bearing can only be accommodated by force, which leads to increased ball loads and cage forces and a reduction in bearing service life. For this reason, the maximum permissible angular misalignment is two minutes of arc. Any misalignment of the bearing rings will result in increased noise during operation.

Cages SKF double row deep groove ball bearings are fitted with two injection moulded snap-type cages of glass fibre reinforced polyamide 66 (fig), ball centred, designation suffix TN9.

Note Double row deep groove ball bearings with polyamide 66 cages can be operated at temperatures up to +120 �C. The lubricants generally used for rolling bearings do not have a detrimental effect on cage properties, with the exception of a few synthetic oils and greases with a synthetic oil base, and lubricants containing a high proportion of EP additives when used at high temperatures.

For detailed information about the temperature resistance and the applicability of cages, please refer to the section “Cage materials”.

Minimum load To achieve satisfactory operation, double row deep groove ball bearings, like all ball and roller bearings, must be subjected to a given minimum load, particularly if they are to operate at high speeds or are subjected to high accelerations or rapid changes in the direction of load. Under such conditions the inertia forces of the balls and cages, and the friction in the lubricant, can have a detrimental effect on the rolling conditions in the bearing arrangement and may cause damaging sliding movements to occur between the balls and raceways.

The requisite minimum load to be applied to double row deep groove ball bearings can be estimated using

where

Frm = minimum radial load [kN]

kr = minimum load factor (see product data)

? = oil viscosity at operating temperature [mm2/s]

n = rotational speed [r/min]

dm = mean diameter of bearing

= 0,5 (d + D) [mm]

When starting up at low temperatures or when the lubricant is highly viscous, even greater minimum loads may be required. The weight of the components supported by the bearing, together with external forces, generally exceeds the requisite minimum load. If this is not the case, the double row deep groove ball bearings must be subjected to additional radial load.

Axial load carrying capacity If double row deep groove ball bearings are subjected to a purely axial load, this axial load should generally not exceed the value of 0,5 C0. Excessive axial loads can lead to a substantial reduction in bearing life.

Equivalent dynamic bearing load

P = Fr when Fa/Fr = e

P = 0,56 Fr + YFa when Fa/Fr > e

The factors e and Y depend on the relationship f0 Fa/C0, where f0 is a calculation factor, see product table, Fa the axial component of the load and C0 the basic static load rating.

In addition, the factors are influenced by the magnitude of the radial internal clearance. For bearings with Normal internal clearance mounted with the usual fits as listed in table T1, T5 and T6, the values for e and Y are listed in table 1

Equivalent static bearing load

P = 0,6 Fr + 0,5 Fa

If P0 < Fr, P0 = Fr should be used.

Deep groove ball bearings | Single row deep groove ball bearings | Basic design bearings | Sealed bearings | Bearings with shields | Bearings with low-friction seals | Bearings with contact seals | ICOS� oil sealed bearing units | Grease life | SKF Energy Efficient (E2) deep groove ball bearings | Deep groove ball bearings with filling slots | Stainless steel deep groove ball bearings | Double row deep groove ball bearings