A multi-operation machine under 846510 performs different machining operations in a single setup without requiring a tool change between operations, and it is specifically designed for wood. A machining center under 846520 is designed for other hard materials such as cork, bone, hard rubber, or hard plastics, and typically incorporates automatic tool-changing capability. The material worked and the tool-change mechanism are the two classification pivots.

Yes. The heading text explicitly includes machines for nailing, stapling, gluing, and similar assembling operations on wood and similar hard materials, captured under 846594 (bending and assembling machines). However, hand-held pneumatic or electric nailers and staplers are classified under the hand-tool heading rather than here.