What unique feature do external lock washers possess?

• A. Internal threading to fit on bolts
• B. A broad surface area for better load distribution
• C. Teeth around the outside edge to help prevent loosening
• D. A wing design for hand tightening

Answer: (C)

External lock washers are specifically designed with teeth around their outer edge, which play a critical role in preventing loosening of bolts and nuts when subjected to vibrations or dynamic loads. These teeth bite into the surface of the assembly they are securing, creating friction that helps maintain torque and stability. This feature is particularly advantageous in applications where movement or vibration is expected, ensuring the integrity of the connection over time.

The other options highlight features that may be associated with different types of washers or fasteners but do not pertain to external lock washers specifically. For instance, internal threading is characteristic of nuts rather than washers, while broad surface areas for load distribution usually pertain to flat washers. A wing design, which allows for easier hand tightening, sounds more like a feature of wing nuts rather than external lock washers. Thus, the distinctive feature of teeth on the external lock washer is what sets it apart in its function.