Length of Key (\( L = \frac{3 \cdot F}{\tau_{allow} \cdot W} \)):

Where:

• \( L \) is the length of the key, in inches.
• \( F \) is the force, in pounds (lb).
• \( \tau_{allow} \) is the allowable shear stress, 25,000 psi.
• \( W \) is the width of the key, in inches.