Feather keys are generally _______
Feather Key Fit Explained
Feather keys are a type of parallel key used in mechanical power transmission. They connect a rotating machine element (like a gear or pulley, called the hub) to a shaft.
Shaft Fit Requirement
The feather key is typically manufactured to be a tight fit within the keyway broached into the shaft. This tight fit ensures:
- The key does not rotate or become loose within the shaft.
- Positive torque transmission between the shaft and the key.
Hub Fit Requirement
In contrast, the feather key is usually designed for a loose fit within the corresponding keyway in the hub (e.g., a pulley or gear). This loose fit allows:
- The hub to slide freely along the length of the shaft.
- Axial movement of the hub while maintaining its rotational drive connection via the key.
This combination of a tight fit in the shaft and a loose fit in the hub is characteristic of feather keys, enabling both torque transmission and axial motion.
Important Questions from Keys
A key having a square cross-section of side d/4 and length l is used to transmit torque T from the shaft of diameter d to the hub of a pulley. Assuming the length of the key to be equal to the thickness of the pulley, the average shear stress developed in the key is given by
The forces experience by a Key used in a gear train for power transmission is
A key of 14 mm width, 9 mm height and 100 mm length is mounted on a shaft of 50 mm diameter. If the allowable shear stress for the key material is 50 MPa, what is the maximum torque that can be transmitted?
- A key of width and height of 6 mm each is used to fix a gear on a shaft of 20 mm diameter. The shaft is used to transmit 10 kW power at 600 rpm to the gear. Permissible shear stress in the key is 80 N/mm$^2$, while compressive stress in the key is neglected. The minimum length of the key, in mm, is _____(round off to 2 decimal places).
- Which of the following key transmits power through frictional resistance only?
