What does the acronym FN stand for in machining?

In machining, the acronym FN stands for "Force fit." This term is used to describe a type of fit between two components where one component is forced into the other to create a tight joint. Force fits are designed to withstand significant loads and typically do not rely on any additional fastening elements like screws or bolts.

This type of fit is commonly seen in applications where parts are to be assembled so that they cannot move relative to each other after assembly. The use of force fits is crucial in ensuring structural integrity and reliability in machined parts, especially in high-stress environments.

In the context of the other choices, friction fit, fine fit, and finish fit refer to different concepts or types of fits that do not capture the essence of FN correctly. Friction fit involves the use of friction to hold components together, fine fit refers to a close tolerance fit that does not necessarily require force, and finish fit usually pertains to the final machining stage to achieve desired dimensions and surface finishes. However, the precision and grip provided by a force fit are key for various mechanical applications, solidifying it as the correct answer for FN in machining contexts.