Abstract
In the present paper, the life tests of 24 ball screws assembled with 66 nylon spacer balls and that of 19 ball screws which differ from the 1st and 2nd reports in the raceway hardness are carried out. Based on the results of these life tests, the influence of use of spacer ball and the raceway hardness on the fatigue life are discussed. The results may be summarized as follows :(1) The basic dynamic load rating of ball screw assembled with the spacer balls is 10% greater than that filled up with the active balls, because the spacer balls reduce the slips between the active balls and raceways. (2) The 66 nylon spacer balls are durable enough for practical usage. (3) The basic dynamic load rating of the ball screws of HRC 56.3 in the raceway hardness of screw shaft is decrease by 20% compared with that of HRC 61. (4) It becomes clear that the fatigue lives of ball screw are considerably influenced by the raceway hardness compared with those of ball bearings from the empirical formula derived in this report.
