A truck-mounted concrete mixer is classified as a motor vehicle under the vehicles chapter rather than here, because the vehicle chassis is the principal element. A stationary or trailer-mounted concrete mixer without a self-propelled chassis classifies under 847431 in this heading. The presence or absence of a self-propelled vehicle chassis is the determining factor.

This heading is limited to machinery working mineral substances—stone, ore, sand, gravel, cement, asphalt, and similar inorganic materials. Machines that sort, grind, or mix food products classify under the food-processing machinery heading, and those working chemicals classify under the chemical-processing machinery heading. The nature of the material the machine is designed to process, not its mechanical action alone, determines the correct heading.