Parallel Keys

Parallel keys come in standard, high, guide, and sliding types. All types are sunk keys: half of the key sits in the shaft keyway, half in the hub keyway. When the hub moves along the shaft, guide or sliding parallel keys are installed — they are used for both sliding and fixed connections and have rounded or flat ends. For a fixed connection between the hub and the shaft, standard and high parallel keys with a round or flat head are used.

Parallel Keys

If the hub moves along the shaft, guide parallel keys are installed; they are fastened to the shaft with screws. For frequent hub movement along the shaft, sliding keys are used, connecting to the hub via a cylindrical projection.

The working face of a parallel key is its narrower side face. The key is elastic and consists of two longitudinal bars: one has a rectangular cross-section and a cutout at the ends, with the bars connected by arc-shaped springs. The load-bearing capacity of the key depends on the thickness of these springs.

Under heavy loads, the key is replaced with one of greater thickness. When arc-shaped springs of considerable thickness are used, the cutout at the ends of the longitudinal bars has to be modified.

Parallel keys have limited application.

Assembly of a parallel key: screws are inserted into the stepped hole and screwed into the threaded hole of the longitudinal bar. A split sleeve spring is inserted into the cylindrical groove, then the longitudinal bars are drawn together with screws until a gap forms — after this the key is ready for operation. When torque is transmitted from the shaft to the hub, the longitudinal gap narrows and the sleeve springs deform. When the torque is removed, the key returns to its initial position.

In wedge keys the gap forms on the side; in parallel keys it forms on top; parallel keys have no taper.

Usually a single parallel key is used in a connection. If the connection strength is insufficient, two or three keys are installed with an angle of 120° or 180° between them. Parallel keys are fitted into keyways on the shaft and do not prevent axial displacement of the parts — for this purpose, shaft shoulders, a locating ring, and a set screw are used.

Parallel Keys

FLOK supplies parallel keys DIN 6885 wholesale and retail in the following sizes: