What does an overarm do on a horizontal milling machine?

The overarm on a horizontal milling machine plays a crucial role by providing support for the arbor, which is the component that holds the cutting tool. Located on the top part of the machine, the overarm extends over the workpiece, allowing for stability and proper alignment during the milling process. This design is essential for achieving precision and accuracy when cutting materials, as it helps minimize vibrations and movement that could affect the quality of the machined surface.

The other options describe functions that are either unrelated to the specific role of the overarm or are associated with different components of the machine. For example, securing the machine to the floor is a foundational requirement but does not relate to the milling operation itself. The rotation during operation pertains more to the spindle or the arbor, and controlling the feed rate is a function managed by the machine's feed mechanisms rather than the support structure of the overarm.