When a German spindle manufacturer needed a coupling that could withstand speeds of 25,000 rpm, it turned to GAM/Jakob to produce it. The resulting torsion-resistant couplings, dubbed the KHS Series, not only met the goal, but has since exceeded it, testing at speeds to 50,000 rpm.

"Metal bellow couplings are simply the best flexible element for high-precision applications," explains General Manager, Craig Van Den Avont, GAM, Chicago. "Especially for those operating at high speeds and requiring high torsional rigidity. While being flexible in axial, lateral, and angular directions, metal bellows offer the highest degree of torsional stiffness at a very low moment of inertia."

The couplings -- with a four-corrugated, stainless-steel bellow and aluminum conical bushing hubs -- offer nominal torque ranging from 133 lb-in. at 0.1 lb-in.2 moment of inertia to a nominal torque of 5,310 lb-in. at 18.07 lb-in.2 moment of inertia.

Due to their high torsional stiffness, the couplings also accommodate misalignments between powertrain components. According to Van Den Avont, even when the initial shaft alignment is nearly perfect, it is only a matter of time before wear, vibrations, or heat knocks them out of line. High-precision servodrives need couplings that not only transmit the motion and torque from one shaft to another, but also make up for misalignment without overstressing the shafts or overloading bearings. KHS couplings, ranging in diameter from 1.56 to 4.8 in., handle a lateral misalignment of 0.004 in. and maximum axial misalignment ranging from 0.02 to 0.028 in. They are said to be maintenance free with durable parts and frictional shaft-hub connections. A press-fit connection method locks bellows to the hub, transmitting torque around the coupling's entire circumference without the need for a keyway.