Chapter 84 is the HS category covering machinery and mechanical appliances and parts thereof, including power machinery, metalworking machine tools, industrial robots, office equipment, automatic data processing equipment, etc. Its core characteristic is machines, equipment, and apparatus used for industrial production, but it excludes electrical equipment (Chapter 85) and transport equipment (Chapter 87). Goods in this chapter usually have power drive, mechanical movement, or energy conversion functions, and it is the main classification chapter for technology-intensive products in international trade. Heading 8461 covers metal cutting machine tools, including machining centers, single-station transfer machines, multi-station transfer machines, and non-cutting metalworking machine tools (such as forging, stamping, rolling, drawing, extruding, thread rolling, tapping, etc.). However, this heading explicitly excludes gear cutting machines, because gear cutting machines (including CNC and non-CNC) are specifically classified under a subheading under heading 8461, and the overall scope of 8461 is metal cutting machine tools, among which gear cutting machines, as a type of cutting machine tool, are listed under a separate subheading. Code 846140 is a 6-digit subheading. The first 2 digits 84 indicate Chapter 84 (nuclear reactors, boilers, machinery, mechanical appliances and parts thereof). Digits 3-4, 61, indicate heading 8461, i.e., metal cutting machine tools, including machining centers, transfer machines, gear cutting machines, etc. Digits 5-6, 40, indicate subheading 846140, i.e., CNC gear cutting machines. Under heading 8461, further subdivision is by processing method: 846120 is other gear cutting machines (non-CNC), 846130 is CNC gear cutting machines (but note that in the actual HS code, 846140 is CNC gear cutting machines, while 846120 is other gear cutting machines). Therefore, 846140 specifically refers to gear cutting machines using CNC technology, such as CNC gear hobbing machines, CNC gear shaping machines, CNC gear grinding machines, etc. This commodity is a CNC gear cutting machine, belonging to metal cutting machine tools and specifically used for processing gears as CNC equipment. Since the HS code sets a dedicated subheading for gear cutting machines under heading 8461, and distinguishes by whether they are CNC: 846120 (non-CNC gear cutting machines) and 846140 (CNC gear cutting machines). Therefore, as long as the machine tool is CNC and used for gear processing, it must be classified under 846140, and cannot be classified under 846120 (non-CNC) or other subheadings of 8461 (such as machining center 846130? Is the actual machining center 846130? Needs verification: Is 846130 a CNC machining center? Actually, the subheading structure of 8461: 846120 other gear cutting machines, 846130 CNC gear cutting machines? No, the correct structure: 846140 is CNC gear cutting machines, 846120 is other gear cutting machines. So CNC gear cutting machines are classified under 846140, and non-CNC under 846120.