8460.40 - Honing or lapping machines:

This category, 8460.40, specifically encompasses honing or lapping machines. These are specialized machine tools designed for finishing surfaces to achieve high degrees of precision and smoothness. Honing machines typically employ abrasive stones or pads that move with a reciprocating or orbital motion to remove a minimal amount of material, refining the shape and surface texture of internal or external cylindrical surfaces, such as bores or shafts. Lapping machines, on the other hand, utilize abrasive compounds applied to a flat or contoured plate to produce extremely flat or precisely shaped surfaces on components.

Unlike sibling categories such as flat-surface grinding machines (8460.31), other grinding machines (8460.39), or sharpening machines (8460.21), honing and lapping machines are primarily distinguished by their function of achieving ultra-fine surface finishes and high dimensional accuracy rather than bulk material removal or shaping. While grinding machines often use rotating abrasive wheels to shape or remove material, honing and lapping focus on the final stages of precision finishing.

Within this category, further distinctions are made to facilitate more granular classification. Subcategories 8460.40.40 and 8460.40.80 differentiate between numerically controlled (NC) machines and other types. Numerically controlled honing and lapping machines are equipped with sophisticated computer systems that precisely control the movement and operation of the machine, allowing for automated and highly repeatable finishing processes. The "other" subcategory covers manual or less automated versions of these machines.