The circumferential ball advance is shown as graphics. It is calculated based on the assumption that the orbit speed of each ball is constant in one section. Because of variation of contact angles the ball orbit speed varies between the rolling element. For calculation is done in the same way as for ball bearings, the lead is not taken into account. A decrease in ball advance means that the next ball is slower and this will lead to forces between the balls. The calculation of orbit speed does not take into account a contact between the balls.