Currently Nook Ball Screws are produced for sale in either one of two ranges, Inch Ball Screw Assemblies and Metric Ball Screw Assemblies. Each of these two Nook Ball Screw ranges is then divided into two categories, based on lead accuracy. The metric range has much greater accuracy than the inch range.
All Nook Ball Screws are either ground ball screws or rolled ball screws. Extremely high temperatures can be detrimental to the production process; however Nook Ball Screws make certain that temperatures are kept below given limits. Only high quality alloy steels are used to produce PowerTrac Nook Ball Screws. The Inch Ball Screw Assemblies can be purchased as XPR, SGT and SRT models. The SRT Nook Ball Screws are created with either stainless steel or rolled alloy as a primary component. They are given a polished finish and they are coated with black oxide for protection. The SRT model has a 0.004 inch per foot lead accuracy and is RC 58-60 case hardened.
The Nook Ball Screw design labeled XPR made using alloy steel and has been precision rolled. It is much more precise than the SRT model with a lead accuracy of 0.001 inch per foot. The finish of this ball screw is also burnished. The SGT Nook Ball Screw is the most precise of all the instruments in this range, with a 0.0005 inch per foot lead accuracy. It is also made from steel alloy and is precision ground.
The Metric Ball Screw Assemblies are composed of the same metals as the Inch assemblies; however they are produced using a different method. In this range there are the MRT and PMT models. The MRT model is constructed to have a lead accuracy of 100 micrometers per 300 millimeters, while the PMT version is designed with a lead accuracy of 25 micrometers per 300 millimeters. button head bolt