What is the primary function of a tapped hole?

The primary function of a tapped hole is to create internal threads for fastening. Tapped holes are specifically designed to allow screws or bolts to be inserted and secured within them, providing a strong mechanical connection between components. This feature is essential in many engineering applications where components must be assembled with precision and strength.

Tapped holes ensure that fasteners can be easily screwed into the material, which allows for repeatable assembly and disassembly without significant wear on the components. This is particularly important for maintenance and repair procedures, making it a crucial aspect of engineering design.

In contrast, the other options do not represent the primary purpose of tapped holes. Providing a flat surface is related to machined surfaces rather than threading; welding pertains to permanently joining parts without threading; and allowing fluid passage describes holes designed for fluid dynamics, not fastening. Thus, the creation of internal threads is the definitive function of a tapped hole.