Ball Screw Jacks Technical Information

Nook ball screw jacks are fitted with Nook's own PowerTrac™ Ball Screws and Nuts.


PowerTrac™ Ball Screws are straight within .010 inch/foot when shipped from the factory, and do not exceed .030 inch in any 6 foot section.

Material Surface Lead Accuracy Screw Dia. Screw Lengths
Alloy black ± .004 in/ft 0.375" to 6.000" up to 24'


A jack assembly uses rolling elements to carry a load similar to an anti-friction (ball) bearing. These elements do not wear during normal use, but rather fatigue. Therefore, ball screw life is predictable and is determined by calculating the fatigue failure of the components.

Proper lubrication, regular maintenance, and operation within specified limits will allow PowerTrac™ Ball Screws to operate to the predicted life.


Backlash (lash) is the relative axial movement between a screw and nut without rotation of the screw or nut. The axial movement between a new PowerTrac™ ball nut and screw will range from .003" to .015" depending on size. Lash in ball screws will remain constant during normal use.

Selective Fit

When less than standard lash (listed above) is desired, ball nuts can be custom-fit to a specific screw with selected bearing balls to minimize lash to .003" to .005" depending on ball size. Select fitting may result in lower life.

Figure 1