Which is the most commonly used work-holding device on a vertical milling machine?

The most commonly used work-holding device on a vertical milling machine is the vise. A vise allows for secure clamping of a workpiece, which is crucial for achieving precise machining operations. It provides stability during cutting processes and can accommodate various sizes and shapes of material.

The design of a standard milling vise often includes adjustable jaws and a main body that can be easily mounted on the milling table, making it highly versatile for different milling tasks. Its ability to firmly grip the workpiece while allowing for easy access by the cutting tool makes it an essential fixture in milling applications.

While hold down clamps, rotary tables, and dividing heads serve specific functions and may be utilized in certain contexts, they do not offer the same level of general utility and ease of use that a vise provides for standard vertical milling operations.