Quill shaft

A quill shaft is a long, slender, often hollow torsion shaft that transmits torque while adding torsional flexibility to a drive line. Its small diameter and long length give a low torsional stiffness, which shifts the system’s torsional natural frequency away from running-speed harmonics and softens torque shocks. In marine gearing a quill shaft runs concentrically inside a hollow gear shaft to drive a remote pinion or to connect a flexible coupling, tuning the shafting torsional response. It is also used in flexible and gear-type couplings to accommodate small misalignment. Sizing balances torque capacity against the flexibility needed to keep critical speeds out of the operating range.