INSIGHT Think big R


olf Steinbock’s eureka moment, which came in 1974 while on a service call to one of his scrap choppers in a US steel mill,


solved at a stroke two basic problems with big bolts. One is that they take a massive amount of torque to tighten. The second is that they have a nasty habit of working loose. When told that the bolts on the gearbox of the otherwise perfectly- functioning scrap chopper required tightening a couple of times a day, Steinbock had a flash of inspiration which he hastily scribbled down on the proverbial napkin. His solution worked perfectly, and the bolts never came loose again. Steinbock’s solution, to split one big


torque into a number of smaller torques, was commercialised as Superbolt. “He was actually surprised that nobody had thought of it before,” says his son, Allan Steinbock, who is the company’s vice- president. Word spread to customers beyond the steel industry and, today, Superbolt’s multi-jackbolt tensioners can be found in a wide range of applications, from satellites to submarines to the Large Hadron Collider at CERN. The problem Steinbock tackled is the


fact that for bolt diameters bigger than about M24, it is very difficult to create enough torque to tighten or loosen a bolt. Simple physics shows that the torque needed to properly pre-stress a bolt increases by the third power of the bolt diameter. Therefore as the bolt diameter increases, the torque requirement for tightening it soars. Traditionally this has required some


heavy-handed methods, but all have their drawbacks. The sledgehammer gives little control, is inconsistent and often causes injuries. Thermal tightening, crane


60 Fastener + Fixing Magazine • Issue 75 May 2012


Words: DavidWiles Photo: Christer Ehrling, Superbolt & CERN


With Superbolt® customers can tighten


even the largest bolts with hand tools. Like the Nord-Lock product range, the result is safer, faster andmore accurate bolting,making thema perfectmatch. Here Nord-Lock takes a closer look at it’s latest acquisition.


wrenching, hydraulic wrenching and hydraulic tensioning can be expensive, inaccurate, time consuming and unsafe.


However, Superbolt tensioners, which


are designed as direct replacements for standard nuts and bolts, allow for the tightening of large bolts with simple hand tools, making bolting more accurate, faster and safer. “The primary benefit of Superbolt is the reduction of torque required,” says Steinbock. “You only need a handheld torque wrench or air tool.” Superbolt tensioners utilise a ring


of hardened jackbolts threaded into a nut body. The Superbolt tensioner is first threaded by hand onto a new or existing bolt or stud. Once positioned, bolt tensioning is accomplished by tightening the circle of jackbolts. A number of different product lines are based on the same basic concept. “Because we are able to generate the


proper preload, we achieve the proper holding power and we don’t have bolts or nuts coming loose, even in high-vibration situations,” says Steve Busalacchi, engineering manager. “This reduces expensive downtime: both downtime required for maintenance to retighten loose bolts, but also downtime caused by studs breaking due to insufficient holding power.” Because Superbolt can be installed


with hand tools, there are also time savings. “We install quicker and we remove quicker,” says Busalacchi. “People’s first impression is that it will take longer because they have several bolts to tighten instead of one. But once they see that you spin it on by hand and perform a quick tightening pattern similar to mounting a wheel on your car with hand-held tools, then they are impressed by the time savings we provide.” The safety benefits of the Superbolt


solution are highly appreciated at a time when many industries have implemented


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