DN Value

DN values allow easy comparison between different ball screw designs. More sophisticated ball return systems result in higher DN values and, conversely, lower DN values are associated with less sophisticated ball return methods. DN values provide direct correlation to ball velocity.

n_max  Maximum speed [rpm]
d_N      Nominal diameter [mm]
DN    Driving speed value

Most ball screws available today have maximum DN values betwen 60,000 and 120,000, and in some cases even higher. However, Steinmeyer recommends observing the maximum speeds published here for each size. Use the following values for orientation purposes and of course for Steinmeyer ball screws only:

• Internal return (Series 1xxx): DN ≤ 120,000
• External return (UltraSpeed and end-cap return) (Series 2xxx and 3xxx): DN ≤ 160,000
• High-load ball screws (UltraThrust) (Series 9xxx with ball diameter 15 mm and 19 mm): DN ≤ 120,000

When using only the DN method to determine maximum rpm for a 3 mm ball screw, the result would be 120,000 / 3 = 40,000 rpm, which is certainly not realistic. The DN method returns unreasonably high numbers when used for very small ball screws! Always check the maximum speed tables.