What size should a pre-drilled hole be compared to the diameter of a machine-threaded rod?

The size of a pre-drilled hole should generally be larger than the diameter of the machine-threaded rod to ensure proper installation and functionality. This larger hole accommodates the threads of the rod and allows for easier insertion without damaging the threads or causing misalignment. Additionally, a larger hole helps to reduce the risk of splitting the material being fastened, which is especially important in wood or similar materials where stress may cause cracking.

Having a hole that is too small could create excessive friction, making it difficult to screw the rod into place, and could potentially damage the threaded rod or the surrounding material. Thus, opting for a hole size larger than the diameter of the rod facilitates a smoother installation process and ensures that the threaded rod can expand or contract without encountering significant resistance.