Mill-turn

Mill-turn combines turning and milling on a single machine. The workpiece sits in a spindle that can rotate for the turning work and can stop or index for the milling work. Machines with a second spindle take the part over and machine the back side as well, with no manual re-clamping.

What it means for the calculation

The gain resembles that of five-axis work: fewer setups, fewer alignment errors and a shorter lead time, because the part does not travel back and forth between lathe and mill. The machine rate and the programming time are higher. On a part that is both round and milled, the calculation moves from two operations with two queues to one operation with one queue. That often saves more in lead time than in machine minutes.

Where it appears on the drawing

Not as a word. It follows from the shape: a round base part with flats, slots, cross holes or off-axis threads points to mill-turn work.

Common mistakes

Pricing a round part with cross holes as turning plus a separate milling operation while a single mill-turn operation is available. Or the reverse: planning mill-turn work while that machine is fully booked, which pushes the lead time up instead of down.

Is mill-turn the same as turning with driven tools?

Driven tools are the simplest form of it; full mill-turn machines have more axes and sometimes a second spindle.

Why a second spindle?

To take the part over and machine the back side without re-clamping it by hand.

Is it always faster than separate turning and milling?

Not always in machine minutes, but usually in lead time.