At Skidmore-Wilhelm we get more support requests related to installing and testing TC Bolts than any other bolting solution. The reason for the higher volume of requests comes down to one thing: lubrication. TC bolts (or twist-off bolts) create a unique testing need because unlike other solutions they rely heavily on lubrication to produce the correct clamp load in a connection. TC bolt installation tools apply a consistent amount of torque when tightening but whether that torque produces the tension required depends on the condition of the fastener’s factory applied lubrication.
TC bolt lubrication can be affected by a variety of things such as exposure to nature’s elements or fluctuating temperatures. Manufacturers can guarantee that their TC bolts are of the highest quality and properly lubricated when they leave their factory but once fasteners are out in the field and exposed to the realities of a job site the responsibility to confirm performance falls on the installer.
The best way to guarantee TC bolt performance is to test them in their current condition and environment prior to installing them in a structure.