Rotating tool. Or rotating part. Different geometries.

Mill-turn machines combine both capabilities on one machine — a CNC lathe with live tooling that enables milling operations. The part rotates like a lathe, but specialized tools can also perform milling, drilling cross-holes, and more without re-chucking. Ideal for parts with both cylindrical and prismatic features (e.g., a shaft with a flat machined on one end, or a flange with holes drilled on the cylinder). Reduces setups from 2 (turn then mill) to 1.

Swiss-type CNC is specialized turning for small-diameter (< 32 mm), long (> 3:1 length-to-diameter ratio) precision parts. The "sliding headstock" provides bearing support close to the cutting action, maintaining rigidity on long slender parts. Ideal for: medical surgical instruments, small shafts, precision bearing races, screw-machine parts. If your part is small and cylindrical with moderate-to-high volume, Swiss type is often the optimal process.

Common. Example: a shaft with a flat machined on the end. Two approaches: (1) Sequential — turn the cylindrical part first, then mill the flat in separate setup. (2) Mill-turn — single setup on mill-turn center with live tooling. Approach 2 is typically faster and more accurate but requires mill-turn machine. For medium-volume parts with combined features, mill-turn wins on time and cost.

For a cylindrical part that could be made either way, turning is typically 30–50% cheaper. A simple shaft: turning 30 minutes/part, milling would require 60–90 minutes. For prismatic parts, milling is the only practical option. Making a prismatic part on a lathe requires creative workholding and is usually more expensive, not less.

Turning typically produces better surface finish due to continuous cutting action — Ra 0.4 µm single-pass achievable on free-machining materials. Milling: Ra 0.8 µm typical single-pass. Both can achieve Ra 0.1 µm with finish passes or secondary operations. For cosmetic cylindrical surfaces (e.g., smooth shaft finishes), turning is preferred. For matching surface finish across prismatic features, milling produces more uniform result.

Turning wins for rotational features (concentricity, runout). Turning a bore and outside diameter in the same setup guarantees excellent concentricity (±0.01 mm typical). Milling equivalent features requires boring from two sides or post-machining operations — concentricity typically ±0.025–0.05 mm. For applications with tight concentricity requirements (motor shafts, precision bearings), turning is the correct process.