ABSTRACT
The prevention of thread galling and the achievement of target thread friction or nut factor are also important issues to be considered. The specification of a low friction lubricant may result in a nut factor that is too low and overtensioning of the fastener. The specification of a lubricant that yields a high nut factor will result in bolt tensions that are relatively low when the fastener is assembled to a specified torque. The selection of a thread lubricant for an existing application should include an evaluation of the assembly process and torque specifications to ensure that final preloads in the assembled fasteners are within the target tension range. The nut factor values in Table 1 include the minimum, mean, and maximum because there is a significant variability in the resultant nut factor that is measured for each set of conditions. The mean value of the nut factor ranges from 0.086 to 0.52. An inspection of the nut factor minimums and maximums in Table 1 shows that some lubricants are more effective than others in reducing the variability in nut factor.
