What does the "B" stand for in the thread designation of ¾" - 10 UNC - 2 - B - LH?

In the thread designation of ¾" - 10 UNC - 2 - B - LH, the "B" indicates a specific type of thread, which in this context refers to an internal thread. This designation is part of the Unified National Screw Thread standard, and the "B" specifically denotes that the threading is for a bolt or internal component rather than a nut or external threading.

Understanding the classification of the threads is essential in applications where components must fit together properly; recognizing internal versus external threading helps ensure compatibility and function in assembly. Internal threads, designated by "B", are typically found in parts that are designed to accept bolts or screws, whereas an external thread would indicate that the component is designed to be threaded into a mating part.

This context helps clarify that while the class and style of threads are important, they do not directly relate to the letter designation "B" which specifically denotes the type of threading as internal.