If very high friction conditions exist while tightening a bolt, the torque being applied can exhibit an oscillatory behavior known as Stick-Slip. It is defined as a periodic oscillation of the torque signal having a series of peaks and valleys. Stick-slip can cause an erroneous detection of target torque or cause an occurrence of the High Torque fault.
Stick-Slip generally results in a low clamp being applied to the joint. It is detected by monitoring when the measured torque has dropped below and then rises above a programmed Stick-Slip Threshold Torque (SSTT) a programmed number of times (n) (default n=1). The detection of Stick-Slip causes the tightening to stop and an error declared.
Monitoring for Stick-slip begins at the tightening step's Torque Threshold (TT) or Snug Torque (Prevailing Torque step) point. If TT is programmed to be less than 10% of the tool's max torque then Stick-Slip may be declared erroneously by Torque noise and create nuisance faults.