8457.20.00 - Unit construction machines (single station)

This classification encompasses unit construction machines, also known as single-station machines. These machines are designed for working metal and are characterized by their integrated structure where all machining operations for a particular workpiece are performed at a single station. They typically consist of a base unit with one or more machining heads that perform specific operations sequentially or in parallel on a workpiece that is held and moved as a single unit.

Distinguishing this category from its siblings, "Machining centers" (8457.10.00) are multi-functional machines capable of performing a variety of operations such as milling, drilling, tapping, and reaming, often with automatic tool changers. "Multistation transfer machines" (8457.30.00) are characterized by multiple machining stations arranged in a line or in a circular configuration, with the workpiece automatically transferred between stations for sequential operations. Unit construction machines, in contrast, are designed for a more specialized set of operations at a single, dedicated station.

Within this classification, further distinctions are made based on the level of automation. Subcategory 8457.20.00.10 specifically covers numerically controlled unit construction machines, indicating those that utilize computer programming to direct their operations. The residual category, 8457.20.00.90, covers all other unit construction machines not equipped with numerical control, which may be operated manually or through simpler mechanical or electrical controls.