Vertical milling machines (VMCs) employ a spindle in a vertical orientation and utilize the power of gravity to remove material from the top of the piece being worked on. Horizontal milling machines (HMCs), on the other hand, use a spindle that’s configured in a horizontal orientation, which allows for uninterrupted production. Most small to mid-sized CNC machine shops, including APM, use VMCs for the majority of their milling operations.