Feather keys are a special type of parallel key designed to allow axial movement of the hub (gear, pulley, or other component) along the shaft while still transmitting torque. This distinguishes them from standard parallel keys, which fix the hub rigidly in both rotational and axial directions.

🔧 Feather Key – Overview

Function: Allows axial sliding without losing the rotational lock between the shaft and the hub.

Application: Common in sliding gears, machine tool spindles, or clutch mechanisms where components need to move along the shaft (e.g., gear shifting).

🔩 Types of Feather Keys

Feather Key Fixed to Shaft (Sliding Hub)

Key is fixed in the shaft keyway (e.g., by screws or fits tightly), and the hub slides over it.

Feather Key Fixed to Hub (Sliding Shaft)

Key is fixed in the hub keyway and slides along the shaft’s keyway.

Feather Key Sliding Freely

The key slides along both the shaft and the hub; often used in loose fits with guiding mechanisms.

⚙️ Design Details

Usually rectangular or square in cross-section.

Standardized by ISO and DIN (e.g., DIN 6885).

Ends may be chamfered for easier insertion and movement.

✅ Advantages

Allows components to engage/disengage or reposition while maintaining torque transfer.

Useful for quick adjustments and variable-speed drives.

❌ Disadvantages

More complex to manufacture than fixed keys.

Can wear over time due to sliding motion.