CNC turning services · Lathe · Mill-turn
CNC turning and mill-turn service
CNC turning services for precision turned parts: shafts, pins, bushings, spacers and threaded fittings on CNC lathes and mill-turn machines, in stainless, brass, aluminum, steel and plastics, from 1 piece.
CNC lathe services for round parts
On a lathe, the part spins and a stationary tool cuts it. That makes turning the fastest and most accurate way to produce anything rotationally symmetric: diameters, faces, tapers, grooves, bores and threads. Concentricity between turned diameters is naturally good because they are cut in one chucking around the same axis.
Typical precision turned parts include motor and drive shafts, dowel and hinge pins, bushings and bearing sleeves, standoffs and spacers, nozzles, knobs, hydraulic and pneumatic fittings, and custom fasteners. Brass C360 and stainless 303 are the classic free-machining turning materials; we also turn 304, 316 and 17-4PH stainless, aluminum 6061 and 7075, steel 1018, 1045 and 4140, titanium Grade 2 and Grade 5, and plastics such as POM, PEEK, nylon and PTFE. See materials for how to choose.
Upload a STEP file and a drawing with the thread callouts and tolerances. An engineer quotes within 12 hours with DFM notes. Standard tolerance is ±0.03 mm; tighter diameters, such as bearing seats with an h6 or H7 fit, are confirmed in the quote.
Mill-turn: turned parts with milled features
Many round parts also need flats, hex sections, cross holes, keyways or off-axis holes. On a plain lathe these would be moved to a mill for a second setup. A mill-turn machine (a lathe with live tooling and often a C axis and Y axis) cuts them while the part is still held in the spindle. This keeps the milled features accurately positioned relative to the turned axis and removes a re-clamp, which is where small parts most often lose accuracy.
Features we turn, and what to know about each
| Feature | Process | Design note |
|---|---|---|
| Outside diameters (OD) | Turning | Best concentricity when all critical ODs are cut in one chucking. |
| Inside diameters (ID), bores | Drilling + boring | Bore depth over about 4× diameter needs a boring bar that may deflect; tolerance gets harder. |
| Grooves (O-ring, retaining ring) | Grooving tool | Use standard groove widths from the O-ring or circlip supplier's table. |
| External and internal threads | Single-point or tap/die | Add a thread relief groove or chamfer at the end; specify class (6g/6H, 2A/2B). |
| Knurls | Knurling tool | Specify pattern (straight or diamond) and pitch; diameter grows slightly after knurling. |
| Tapers and chamfers | Turning | Give angle and one reference diameter, not two diameters and a length that conflict. |
| Cross holes, flats, hex, keyways | Live tooling (mill-turn) | Done in the same chucking, positioned relative to the turned axis. |
| Face features, off-axis holes | Live tooling, C/Y axis | Bolt circles on a flange can be cut without moving to a mill. |
Design tips for CNC turned parts
Keep length-to-diameter in check
Slender parts deflect away from the tool. Up to about 3:1 length-to-diameter turns easily in a chuck. Beyond that, the part needs tailstock support or a steady rest, and above roughly 8:1 holding tight diameters along the full length gets difficult. If a long shaft only needs accuracy at bearing seats, say so on the drawing.
Add thread relief and chamfers
A thread cannot run fully up to a shoulder. Add an undercut groove or allow a few incomplete threads. A 45° chamfer at the start of every thread protects the first turn and helps assembly.
Internal corners and groove bottoms
Turning inserts have a nose radius, commonly 0.2–0.8 mm. Allow a small radius in internal corners unless a sharp corner is needed for a mating part, in which case specify an undercut.
Blind bores
Drilled holes end in a 118° or 140° cone point. If you need a flat bottom, specify it, and expect it to cost more. Keep blind bores shallow where possible.
Pick the material for the process
Brass C360 and stainless 303 machine fast and give clean threads. 304 and 316 are tougher and work-harden, so they take longer. If the part does not need 316's corrosion resistance, 303 often lowers cost. Read more in stainless steel machining.
Finishes for turned parts
Common finishes are passivation for stainless, zinc or nickel plating for steel, and anodizing for aluminum. Masking threads or fit diameters from coating is possible; mark the masked areas on the drawing. See surface finishes.
Related
Other processes and services
CNC milling
Prismatic parts, housings and multi-face work.
10 – 1,000 pcsLow-volume production
Batches of turned parts with first-article approval.
Reports · first articleQuality
Inspection reports with critical dimensions on every order.
OverviewCNC machining in China
How ordering, shipping and payment work.
FAQ
CNC turning questions
What is the difference between CNC turning and mill-turn?
CNC turning cuts rotating parts with stationary tools. Mill-turn adds live (driven) tools, so flats, cross holes and off-axis features are milled in the same setup without moving the part to a separate mill.
What tolerance can you hold on turned diameters?
Our standard is ±0.03 mm. Tighter tolerances, such as bearing fits, are possible when called out on the drawing and confirmed in the quote.
Which threads can you cut?
Metric and inch threads, internal and external, such as M8×1.25 or 1/4-20 UNC. Specify the standard and class on the drawing, and any special forms like pipe threads.
Can you make a single turned part?
Yes. The minimum order is 1 piece, and runs go up to around 1,000 pieces.
Which material is cheapest to turn?
Free-machining grades such as brass C360, stainless 303 and aluminum 6061 cut fastest. Tough grades like 316, 17-4PH and titanium take longer and cost more per part.