What is Stick Slip?
Stick-slip is the condition where the screw, instead of rotating uniformly as torquing continues, begins to show a stop-start pattern. When this happens, the torsioning effect on the screw is being absorbed as excess friction between the threads or the underside of the head and the mating parts of the collar, instead of contributing to the stress in the joint of the elements. If the stresses are low, the collar will not achieve the full holding power and could potentially cause a failure.
The proprietary black oxide finish on our carbon steel collars and couplings is formulated as part of the total performance of the product. It affects the holding ability of the collar/coupling, the anti-stick-slip characteristic and helps to keep the torque rating of the screw within its designed parameters. It also provides corrosion protection, although it is not intended to be used as an outside weather protective finish.