Red Seal Machinist Practice Exam

What is a common characteristic of high-speed steel (HSS)?

1. It is brittle and breaks easily

2. It maintains sharpness at high temperatures

3. It tarnishes quickly when exposed to moisture

4. It is only used for non-metal materials

The correct answer is: It maintains sharpness at high temperatures

High-speed steel (HSS) is renowned for its ability to maintain sharpness and hardness at elevated temperatures, making it a preferred material for cutting tools. This property is due to its unique composition, which includes elements such as tungsten, molybdenum, and chromium. These alloying elements enhance the hardness and toughness of HSS, enabling tools made from this material to perform effectively even under the high temperatures generated during machining operations. As a result, tools made from HSS can cut through metal without losing their sharpness, allowing for more efficient and precise machining. The other characteristics presented are not attributes of HSS. For instance, while some materials may be brittle, HSS is actually designed to be tough and durable, resisting breakage under normal operating conditions. Additionally, HSS does not easily tarnish when exposed to moisture; it has good corrosion resistance due to its alloying elements. Lastly, HSS is primarily used for machining metals and is not limited to non-metal materials, making it a versatile option in metalworking applications.