Load ratings are expressed in Kgf (kilogramme force)on this website. That is the force exerted by a mass of 1 kilogramme at the Earth's surface. You will often see force expressed in Newtons elsewhere. A Newton is defined as the force that will accelerate a mass of one kilogram at the rate of one meter per second per second (or 1 m/s²). Since the force of gravity at the Earth's surface is 9.80665 m/s², 1 Kgf = 9.80665 Newtons but, to keep it simple, we say 1 Kgf = 10 Newtons.
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Dynamic load rating
The official explanation for this is... "The dynamic load rating is that constant stationary radial load which 90% of a group of identical chrome steel bearings, with only the inner ring rotating, can endure for one million revolutions before the first signs of fatigue develop". Yes, 1 million revolutions sounds a lot but is it really? If you take a bearing running at 5000 rpm with the max dynamic load applied to it, it will last for 1,000,000 revs divided by 5000 = 200 minutes or 3 hours and 20 minutes!! This should tell you that these figures are used in the calculation of life ratings but bearings should not be subjected to such loads in normal application unless you don't expect them to last very long. AISI440C/KS440 stainless steel bearings will achieve approximately 80% of the figure quoted. For life ratings, please contact SMB. |
Static load rating
This rating represents the purely radial load which will cause a total permanent deformation of the balls or raceway equal to one ten-thousandth of the ball diameter. This may be tolerable for certain applications but not where any smoothness or accuracy is required. Static load ratings for stainless steel bearings are approximately 75% of the load ratings for chrome steel bearings.
The load capacity of a bearing may be limited by the lubricant. Certain lubricants are only suitable for light loads while others are designed for high load applications. Load ratings are higher for full complement bearings (see Retainer). The axial load capacity of a radial ball bearing can be increased by specifying loose radial play. |
Axial load rating
 Small and thin-section deep groove ball bearings should not be subjected to axial (thrust) loads greater than 25 percent of the bearing's static load rating. For larger bearings (e.g. 6001, 6201, 6301 upwards) the figure rises to nearer 50 percent. To exceed the recommended limits will have a detrimental effect on bearing life. |
