Millwright Level 1 Practice Exam

What characteristic do Acme threads have?

1. 24 degree angle with rounded roots

2. 29 degree angle with flat root and crests

3. 30 degree angle with rounded roots

4. 32 degree angle with pointed crests

The correct answer is: 29 degree angle with flat root and crests

Acme threads are distinguished by their specific design features that enhance their usability in various mechanical applications. The correct answer highlights that Acme threads have a 29-degree angle with flat roots and crests. This geometry allows for better load-bearing capabilities and reduces wear, making it ideal for applications that require high strength and stability, such as in lead screws for machinery. The flat root and crest design contribute to a larger surface area for contact, which improves the thread's ability to withstand lateral loads and provides more effective engagement between mating components. This is particularly important in power transmission mechanisms where load distribution is crucial for performance and longevity. In contrast, other thread designs mentioned, such as those with different angles and shapes, serve specific purposes but do not embody the characteristics that define Acme threads. For instance, rounded roots might be found in different thread profiles that prioritize other factors like ease of manufacturing or finer adjustments. Thus, understanding the unique specifications of Acme threads aids in recognizing their application in mechanical systems.