Turning is the oldest production process still in daily use and the cheapest way to make anything round. The workpiece spins in a chuck or a collet while a single fixed cutting edge travels along it, so material comes off continuously and the finish is good straight off the machine. Anything with an axis of rotation belongs on a lathe before it belongs on a mill.
What the process actually does
A lathe holds bar or billet in a rotating spindle and drives a tool along two axes: parallel to the axis of rotation and across it. That gives diameters, faces, tapers, grooves, threads and bores in a single setup. A live tooling lathe adds driven spindles so cross holes and flats happen without a second machine, and that is where most of the saving on a turned part comes from.
How a shop prices a turned part
Three numbers drive the quote: cycle time, setup time and material. Cycle time is close to fixed for a given geometry, so quantity spreads the setup rather than the cut. Bar fed production on a machine that runs unattended is priced very differently from a one off chucked in a manual lathe, which is why one drawing can come back at ten times the unit price from two honest shops.
When turning is the wrong answer
If the part is mostly prismatic, carries features on five faces, or its round features are incidental to a block of material, milling wins. If the walls are thin enough to chatter or push away from the tool, turning gets slow and tolerances drift. Below a certain diameter to length ratio the bar whips, so a long slender shaft needs support, a sliding headstock machine, or a different design.
What to send with the drawing
Send a solid model plus a dimensioned drawing that says which diameters are critical and which are stock. Name the material by specification rather than by nickname. State the surface finish where it matters and leave it off where it does not, because an unnecessary finish callout on a non functional diameter adds a pass to every part you will ever buy.
Questions people ask about cnc turning
What is CNC turning in one sentence?
It is machining on a lathe under numerical control: the part rotates, a fixed cutting tool moves against it, and the machine repeats the same path on every piece without an operator steering it.
Is turning cheaper than milling?
For round parts almost always, because material comes off continuously rather than in interrupted cuts and the cycle is shorter. For anything that is not fundamentally round, the extra setups needed to make a lathe do the job cancel the advantage.
What tolerances should I expect on a turned part?
General machining practice holds diameters comfortably within a few thousandths of an inch with no special measures. Tighter than that is achievable and is priced as a separate operation, often a grind after turning, so call out the tolerance only where function needs it.
Can one shop turn and mill the same part?
Yes, and it is usually cheaper. A mill turn or multi axis lathe completes the part in one holding, which removes a setup, removes a re fixturing error, and removes the handling time between two machines.