Which milling machine allows vertical-plane table tilt via a knee swivel? Considering common machine tool types, identify the machine whose table can be tilted in the vertical plane using a swivel mechanism at the knee (in addition to a horizontal swivel).

Introduction / Context:
Machine tool versatility is defined by available swivels and tilts. A universal mill has a horizontal swivel table for helical work, while the omniversal extends adjustability by adding a vertical-plane tilt at the knee.

Given Data / Assumptions:

• Distinguishing between “universal” and “omniversal.”
• Looking specifically for vertical-plane tilt at the knee, not just horizontal swivel.

Concept / Approach:
A universal milling machine’s hallmark is a table that swivels about a vertical axis (horizontal-plane swivel). The omniversal milling machine adds an additional swivel (or hinge) at the knee to tilt the table in a vertical plane, enabling compound angle machining and complex helixes not possible on a standard universal mill.

Step-by-Step Solution:
Identify the required feature: vertical-plane tilt at the knee.Match with machine types: only the omniversal provides both horizontal swivel and vertical tilt via knee arrangement.Therefore, select omniversal milling machine.

Verification / Alternative check:
Manufacturer catalogs show omniversal machines with dual swivels, often depicted with tilt scales at the knee.

Why Other Options Are Wrong:

• Universal: horizontal swivel only.
• Plain: neither horizontal nor vertical swivel at the table.
• Hand/turret mill: may tilt the head, not the table via a knee swivel as specified.

Common Pitfalls:
Assuming “universal” means fully adjustable in all planes; confusing head tilt with table/knee tilt.

Final Answer:
Omniversal milling machine