Both headings cover machines performing multiple operations, but 846520 is specifically limited to machining centers for cork, bone, hard rubber, hard plastics, or similar hard materials — explicitly excluding wood. Heading 846510 covers multi-operation machines for wood and similar materials that operate without a tool change. If the machine is designed for wood, it belongs in 846510 or another 8465 subheading; if it is a machining center for the non-wood hard materials listed, 846520 applies.

Classification of dual-purpose machines follows the machine's principal use or, where that is ambiguous, the heading that most specifically describes it. CBP may require technical documentation — manufacturer specs, tooling configurations, and commercial invoices identifying the primary substrate — to resolve the classification. Seeking a binding ruling from CBP before importation is advisable for machines marketed for multiple material types.