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GRW High Precision Ball Bearings

High precision ball bearings in grades up to ABEC 9 with bores from 1 to 30mm and comparable inch dimensions

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bearing capacities

Static bearing capacity

In rolling bearing technology, we talk about the static bearing capacity when the ball bearing is loaded while stationery or during slow swinging movements. The calculations are made according to DIN ISO 76.

Basic static radial load rating Cor

The basic static radial load rating is the static radial load which corresponds to a calculated contact stress of 4200 MPa at the centre of the most heavily loaded rolling element/raceway contact.

Static equivalent radial load Por

The static equivalent radial load is the static radial load which would cause the same contact stress at the centre of the most heavily loaded rolling element/raceway contact that occurs under the actual load conditions.

Calculating the static equivalent radial load:

Por = Xo . Fr + Yo . Fa
Xo  = 0.6
Yo  = 0.5
F  = greatest radial load occurring (N)
Fa   = greatest axial load occurring (N)

If the calculation gives a value, Por < Fr, Por = Fr should be set.

Permanent deformation

Permanent deformation on raceways and rolling elements even occurs when a stationery ball bearing is only loaded moderately.

Experience shows that a deformation of 0.0001 x rolling element diameter on the most highly loaded point of contact between raceway and rolling elements will not noticeably effect the function of the ball bearing.

Even greater deformation is justifiable if the ball bearing is running at low speed and the requirements for noise are not high. On the other hand only slight permanent deformation is allowed if the noise and friction requirements are particularly stringent.

Dynamic bearing capacity

The dynamic bearing capacity is the stress on a rotating ball bearing. The additional term ‘dymanic’ indicates the operating condition of the bearing not the effect of the load. The calculations are made according to DIN ISO 281.

Basic dynamic radial loading Cr

The basic dynamic radial load rating for radial ball bearings is that constant radial load which a sufficiently large number of apparently identical ball bearings could theoretically endure for a basic rating life of one million revolutions.

Dynamic equivalent radial load Pr

The dynamic equivalent radial load for radial ball bearings is that constant radial load under the influence of which a rolling bearing would have the same life as it will attain under the actual load conditions.  

The DIN load ratings are given in the ball bearing tables. The actual load ratings can deviate depending on the ball bearing type. The load ratings are approximately 30% lower for hybrid ball bearings than for comparable steel ball bearings.

Please contact us for the exact load ratings.


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