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If you are sourcing turned components, the first question on the drawing is usually the tolerance question. The short answer: a capable shop holding standard production work on a multi axis cnc turning center will hold around ±0.012 mm (±0.0005 in) on turned diameters, ±0.005 mm (±0.0002 in) on precision features, and down to ±0.002 mm (±0.00008 in) on critical dimensions under controlled conditions. What you actually get on your part depends on the machine configuration, the feature type, the material, and how many times the part has to be clamped. This article breaks each of those down so you can specify tolerances with confidence.
Not all lathes are equal. A basic 2-axis lathe (X and Z only) is fine for straightforward shafts and flanges, but every off-center feature forces a second setup on a mill, and each re-clamping adds positioning error. Turn-mill centers with C-axis, Y-axis, and live tooling keep the part in one chucking, which is the single biggest factor in holding tight, repeatable numbers.
| Machine configuration | Typical production tolerance | Best achievable tolerance |
|---|---|---|
| 2-axis CNC lathe | ±0.025 mm (±0.001 in) | ±0.012 mm (±0.0005 in) |
| Multi-axis turn-mill center (C / Y axis, live tooling) | ±0.012 mm (±0.0005 in) | ±0.005 mm (±0.0002 in) |
| High-end multi-axis / Swiss-type, temperature-controlled | ±0.005 mm (±0.0002 in) | ±0.002 mm (±0.00008 in) |
These ranges assume a rigid machine, a sound process, and a competent operator. They are also per-feature numbers: holding ±0.005 mm on one diameter is very different from holding it across every dimension of a complex part.
A drawing rarely asks for one blanket tolerance. Here is what a well-run multi-axis turning process realistically holds on the features that matter most:
Two shops can quote the same tolerance and deliver very different results. The difference comes down to five factors:
1. Number of setups. Every time a part is unclamped and re-fixtured, datum shift creeps in. A part turned on one machine and milled on another carries the sum of both fixtures' errors. Single-setup machining on a turn-mill center removes that stack-up entirely, which is why geometry-critical cnc turning parts should always be finished in one clamping wherever possible.
2. Material behavior. Free-machining aluminum and brass hold fine finishes and tight sizes with ease. Stainless steel work-hardens and deflects. Titanium concentrates heat at the cutting edge and moves as it cools. Engineering plastics like PEEK expand with heat and relax after machining, so tolerances below ±0.01 mm on plastic need careful process planning and often a stress-relief cycle.
3. Part geometry. Slender shafts with a high length-to-diameter ratio deflect under cutting pressure; thin-walled tubes distort under chucking force. Both are machinable to tight tolerances, but only with the right support (steady rests, tailstocks, soft jaws) and reduced depths of cut.
4. Machine rigidity and thermal stability. Positioning accuracy on high-end platforms reaches a few microns, but that number degrades fast in a shop without temperature control. A 100 mm steel part grows roughly 1.2 µm for every 1°C rise — so ±0.002 mm work is meaningless without a controlled environment and warm-up cycles.
5. Tooling and process control. Insert wear drifts dimensions over a production run. Shops holding ±0.005 mm all day rely on tool-wear compensation, in-process probing, and SPC monitoring rather than end-of-run inspection alone.
Tighter tolerances cost money exponentially, not linearly. A few practical rules:
At ANOK Precision Manufacturing, our turning department runs nearly 15 CNC turning machines 20 hours a day, covering parts up to 520 mm in diameter and 3,600 mm in length. Our precision cnc turning work routinely holds tolerances down to ±0.002 mm on critical features, in materials from aluminum and stainless steel to titanium (Ti-6Al-4V), Inconel, and PEEK. As an ISO 9001:2015 certified factory, we back those numbers with in-process inspection, CMM verification, and full traceability for medical, aerospace, and automation programs. Send us your drawing, and our engineers will confirm exactly which tolerances we can hold — and where a small design tweak could save you money.