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Precaution: Ball Screw Selection

Please check the following conditions when you select and examine NSK Ball Screws.

1. In case of oscillating motion

If the rolling elements do not rotate all the way, but only halfway, and if this minute stroke is repeated, lubricant disappears from the contact surface of rolling elements and raceways, and metallic parts directly make contact each other. This generates "fretting," a premature wear. Fretting cannot be entirely prevented, but it can be mitigated.

  • Grease which prevents fretting is recommended.
  • Even when standard grease is used, the life can be markedly prolonged by adding a long stroke once every several thousand cycles. (The rotation speed would be more than twice the effective turns of balls. For example, be more than 5 rotation in the case that the effective turns of balls is 2.5.)

2. When an extraordinary heavy load is applied during stroke

When an extraordinary heavy load is applied during stroke, the actual life could be extraordinarily shorter than the calculated life. In such a case, the contact pressure to the balls/rollers and the rolling contact surface is extraordinarily high.

  • Please examine the life in view of the contact pressure.