CNC Turning in China for Shafts, Bushings, and Threaded Parts

CNC turning is used to make predominantly rotational geometry: outside and inside diameters, shoulders, grooves, bores, and threads on parts held in a chuck or collet while the workpiece rotates. Typical buys include shafts, pins, sleeves, bushings, fittings, and spacers. When the design is mostly prismatic flats and pockets, milling is often primary; many assemblies combine turned and milled features.

Specify turning when the critical features are concentric around an axis—diameters, bores, threads, and smooth cylindrical surfaces. Specify milling when you need pockets, ribs, bosses, or multi-sided prismatic work with the blank largely fixed. If your print mixes both, we sequence operations so tolerances and cost stay under control.

We support facing, straight OD turning, boring and ID finishing, grooving, profiling, threading (external and internal), chamfers, and cut-off from bar when the design allows. Operations are combined in one program where possible so length, diameter, and thread relationships stay aligned.

Cost and schedule depend on material machinability, length-to-diameter ratio, thread complexity, tolerance bands, inspection level, and lot size. Slender parts and tight threads usually need more conservative passes and more metrology. We quote all of that explicitly so the price matches the risk, not a generic hourly rate alone.

We turn aluminum grades such as 6061 and 7075, stainless including 304 and 316L, alloy and carbon steels, brass and copper alloys, titanium, and engineering plastics such as acetal, nylon, and PEEK where lathe stability allows. Grade choice affects inserts, speeds, and coolant—so we align material to your environment and any plating or heat treatment downstream.

Standard tolerance on turned features is ±0.05 mm, and ±0.01 mm is available on the features that genuinely need it—tolerance those individually on the print. Dimensions you do not tolerance yourself fall under the general tolerance class you nominate; we work to ISO 2768 as the reference. Achievable bands still depend on stick-out, interrupted cuts, and material. For threads, 6g external and 6H internal cover commercial metric work, and 2A external with 2B internal cover Unified; threads are checked with gauges or functional samples when assembly risk is high. We document first-article or in-process checks to match your incoming inspection plan.

Send STEP, STP, IGES, or IGS solids when possible. Add PDF or DWG drawings for threads, GD&T, surface finish, and notes not fully modeled. For long shafts, a section view with stack-up dimensions reduces ambiguity and speeds programming.

Standard lead time on turned work is 10 to 15 days, and 7 days is the fastest we run—on a mini order, once material, inserts, and gauging are aligned. Production timing scales with quantity, thread scope, and finishing. You get a confirmed window during quoting—not a guess after the order is placed.

Turned parts are handled within 400 mm diameter. The more useful distinction is bar work versus chuck work: bar-fed automatic machines as a class are generally limited to under 60 mm diameter, while chuck and blank work reaches the full 400 mm. So a long slender part and a large flanged part are two different conversations even when both are round. Send the outside diameter, the overall length, and where the critical features sit, and the quote will name the route.

ISO 2768-1 sets general tolerances for linear and angular dimensions that carry no individual tolerance indication, in four classes—f fine, m medium, c coarse, v very coarse—for parts made by metal removal. It only governs the dimensions you leave untoleranced; anything you tolerance yourself overrides it completely. As a feel for the numbers, over 6 up to 30 mm nominal, class m permits ±0.2 mm and class f permits ±0.1 mm. Indicate the class in or near the title block. One clause is worth knowing: unless stated otherwise, a workpiece exceeding the general tolerance does not automatically get rejected, provided its ability to function is not impaired.

A live or driven tool has its own power source and can rotate while the lathe spindle is stationary; it mounts in the turret alongside standard turning tools. Paired with a C axis, which positions the spindle in step with those tools, it brings slot milling, keyways, face drilling and drilling on the part circumference into the same setup as the turning—which removes a second fixturing and the datum transfer that comes with it. Whether your part needs that depends entirely on its off-axis features. Call them out on the RFQ and the quote states how the part is routed and how many setups it takes before you release a PO.

For metric work, 6g external and 6H internal are the classes the standard flags for commercial nut and bolt threads. For Unified work, 2A external and 2B internal are the most commonly used for general applications including bolts, screws and nuts. Classes 1A, 2A and 3A apply to external threads only; 1B, 2B and 3B to internal only. The choice is driven by length of thread engagement—short, normal or long—and by quality requirement: fine for precision threads where little variation of fit is acceptable, medium for general use, coarse where manufacturing difficulty is expected such as threading hot-rolled bars or long blind holes. Two things worth adding to the print: the required number of full threads, and a chamfer on the leading threads of both the male and female part.

Finish on a turned diameter is a function of feed and tool corner radius. With a 0.8 mm corner radius, roughly 0.10 mm/rev gives about Ra 0.4 µm and 0.30 mm/rev gives about Ra 6.3 µm; a 0.4 mm radius needs proportionally lighter feeds for the same bands. Those are theoretical values—rigidity, material and tool condition move the real result. The cost boundary sits around Ra 1.6 µm: that finish and coarser is obtainable at reasonable cost through general roughing and semi-finishing, while anything finer needs operations added purely to refine the surface. One consistency check: roughness on a diameter should stay under about one-eighth of the dimensional tolerance on that diameter, or the finish stops supporting the size control you asked for.