The holding power of a sunk key is due to its resistance to what?

• A. Shear
• B. Shear and crushing
• C. Crushing
• D. Tension and shear

Answer: (B)

The holding power of a sunk key is primarily due to its resistance to both shear and crushing forces.

Shear refers to the force that attempts to slide the key parallel to the surface of the keyway, and its resistance to this force is critical for ensuring that the key remains securely positioned, thus preventing relative movement between the components it is securing.

On the other hand, crushing refers to the force experienced perpendicular to the key, which can cause deformation if the fit is too tight or the material is too weak. The sunk key must withstand this compressive force to maintain its integrity and ensure it functions effectively within the assembly.

Therefore, the correct answer encompasses both shear and crushing forces, highlighting the importance of both types of resistance in ensuring the key's effective holding power.