Keyed vs. Threaded Bushing Ends: Choosing the Right Power Connection

Torque has to get into and out of the bushing somehow, and there are three common ways to do it. Keyed ends use a machined keyway and a parallel or Woodruff key — simple, serviceable, and forgiving of moderate misalignment. Threaded ends clamp a hub or coupling axially and are common on pump and agitator bushings. Press-fit journals rely on diametral precision and an interference fit to carry torque without any hardware at all.

Keys are the American workhorse: cheap, repairable, and everywhere — but keyways introduce stress concentration and a fatigue penalty at high reversal counts. Threaded ends resist axial movement and allow repeated assembly, but require care with torque specs to avoid galling. Press fits are the cleanest option dynamically but demand tight tolerances and controlled assembly temperature.

The failure disasters happen at the interfaces: a key sized for one bushing rating mated to a hub cut for another, or a threaded end over-torqued against a shoulder that was never designed to take the load. Always confirm the end-feature spec on your bushing drawing before ordering mating hardware, and never mix connection philosophies within one joint.

Our keyway and threading reference chart (above) lists the standard keyway dimensions, thread specs, and retaining ring groove sizes cross-referenced by bushing diameter.