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-60% Mass
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Silicon Nitride balls are 60% lighter than steel. As the RPM of a bearing increases, the centrifugal forces imparted on the outer raceway by the ball increase, ultimately causing fatigue failure of the steel. The lighter weight silicon nitride reduces the stress on the raceway allowing for higher speed capabilities. Similarly, the gyroscopic moment created by the X, Y, Z motion of the ball is significantly reduced at higher speed, which results in less ball skidding in the bearing. Skidding is a major source of internal heat generation and raceway wear.
The limiting speed of any bearings is due to the ball's centrifugal force which inhibits pure rolling of the balls. At high speeds, the balls generate high centrifugal forces which are superimposed on the bearing preload. As speed increases, this effect produces more friction and heat generation, accompanied by increased surface stress at the contact area. Silicon Nitride balls greatly reduce this effect in the bearing allowing for higher speeds and lower raceway wear.
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