Generally, a machine is classified by its essential character or primary operating principle. If the machine's core metalworking function is driven pneumatically or hydraulically and the electrical components are merely ancillary (e.g., a control panel), it may still qualify as nonelectric. However, if the electric motor is the primary driver of the metalworking action, an electric heading would be more appropriate. CBP guidance or a binding ruling can resolve ambiguous cases.

Aerospace assembly (pneumatic riveting and fastening tools), heavy equipment manufacturing (hydraulic press-fit and forming fixtures), and shipbuilding (mechanical metal-working rigs) are among the primary end-use sectors. These industries favor nonelectric systems in environments where electrical spark risk is a safety concern or where compressed-air infrastructure is already in place.