A shaft key works by providing a mechanical connection between a rotating shaft and a hub or other rotating component, effectively preventing slippage and allowing for torque transmission.
Here's a breakdown of how it works:
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Key Components: The system consists of three main parts:
- Shaft Key: A small, standardized piece of metal (often rectangular or square) designed to fit into keyways.
- Keyway (or Keyseat): A slot or groove machined into both the shaft and the hub (or the component being connected to the shaft). The keyway's dimensions match those of the shaft key.
- Shaft and Hub: The shaft is the rotating element that delivers power, and the hub is the part connected to the shaft (e.g., a gear, pulley, or sprocket).
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Assembly: The shaft key is inserted into the keyway on the shaft. The hub, with its own keyway aligned, is then slid onto the shaft, positioning the key within both keyways. This creates a locking mechanism.
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Torque Transmission: When the shaft rotates, the key, locked into both the shaft keyway and the hub keyway, forces the hub to rotate along with the shaft. Torque is thus transmitted from the shaft, through the key, and into the hub (or other connected component).
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Preventing Slippage: Without a shaft key, the hub would likely slip on the shaft, especially under load. The key creates a positive engagement, ensuring that both components rotate together at the same speed.
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Shear Force: The key is subject to a shear force, which is the force attempting to "cut" or shear the key across its cross-section. The key's material and dimensions are chosen to withstand the expected shear forces.
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Types of Keys:
- Square Key: Simple and common.
- Rectangular Key: Similar to square keys but with different dimensions.
- Woodruff Key: A semi-circular key often used in applications where precise alignment is required or when the keyway depth is limited.
- Gib-Head Key: Has a "head" that facilitates removal.
Here is a simple table summarizing the key parts:
| Component | Function |
|---|---|
| Shaft Key | Connects the shaft and hub, transmitting torque. |
| Keyway | The slot cut in the shaft and hub that accepts the key. |
| Shaft & Hub | The rotating components connected by the key. |
In summary, a shaft key acts as a bridge between the shaft and the component attached to it, ensuring synchronized rotation and efficient torque transfer, thereby preventing slippage.
