- The short answer: ±0.003 mm on CNC milling, ±0.002 mm on CNC turning, ±0.002 mm where precision grinding or wire EDM is used, but the number on the quote is confirmed per feature, not assumed from a headline.
- Tolerance is a property of the feature, not the machine. The same 3-axis centre holds a ±0.05 mm general edge easily and fights for ±0.003 mm (milling) / ±0.002 mm (turning) on a long thin wall.
- ISO 9001:2015 / IATF 16949:2016 / ISO 14001:2015, certificate numbers published and verifiable.
- Build-to-print work: the plant cuts to your design and reports against your drawing.
- No minimum order, prototype and production run on the same machines.
The direct answer and why it is not one number
The honest answer to "what tolerance can 3-axis CNC machining hold" is two numbers plus a condition. The plant holds ±0.003 mm on CNC milling, ±0.002 mm on CNC turning and ±0.002 mm where precision grinding or wire EDM is used. Those are real, repeatable figures on features that suit the process. The condition is that the figure is confirmed against the actual geometry at quote stage, because tolerance is decided by the feature you are measuring, not by the axis count of the machine that made it.
A 3-axis centre with a ±0.003 mm (milling) / ±0.002 mm (turning) positioning capability will hold a ±0.05 mm edge on a rigid block without thought, and will hold ±0.002 mm on a short, well-supported bore. Put the same ±0.002 mm on a 200 mm-long thin wall and the part will wander before the machine does. That is the whole point of asking the question properly: you are really asking what this feature can hold, and the answer depends on the factors below.
What "tolerance" actually measures
A tolerance is the band within which a dimension must fall to be accepted. On a drawing it is a number; on the floor it is the difference between where the cutter actually went and where it was told to go, accumulated across every step from stock to finished feature. Understanding what fills that band is what lets a buyer ask for the right tolerance instead of a safe-sounding tiny one.
Five things fill the band on a 3-axis part, in roughly this order of influence:
- Datum structure. Every feature is measured from a datum. If the part is located and re-located through several setups, each re-clamp adds its own repeatability to the stack. A tolerance on a feature far from the datum is only as good as the chain that locates it.
- Tool deflection. A long, slender end mill bends under cutting load. The deeper or the harder the cut, the more it bends, and the more the finished dimension drifts from the programmed one.
- Thermal growth. Spindle, stock and fixture all expand as heat builds through a run. A dimension cut cold and measured warm can differ by microns, which is why critical features are often measured on a temperature-controlled inspection bench, not at the machine.
- Feature size and aspect ratio. A shallow pocket reachable with a short stiff tool holds tighter than a deep slot that forces a long flexible one.
- Material behaviour. Free-machining aluminium moves less than work-hardening stainless or springy titanium under the same cut.
What tolerance is achievable, by method
The table below is the working guide used at quote stage. It is a capability envelope, not a promise, the final figure is still confirmed against the specific drawing.
| Method / feature | Typical as-held tolerance | What limits it |
|---|---|---|
| 3-axis milling, general features | ±0.05 mm to ±0.01 mm | Datum chain and tool deflection |
| 3-axis milling, supported criticals | ±0.003 mm | CMM verification, slow feeds |
| CNC turning, diameters | ±0.002 mm | Spindle run-out, tool wear |
| Precision grinding | ±0.002 mm | Wheel dress and roundness |
| Wire EDM | ±0.002 mm | Wire path and spark gap |
| Hole-to-hole position (CMM) | ±0.01 mm typical | Fixture repeatability |
| Flatness / perpendicularity (GD&T) | 0.01–0.02 mm | Bed and fixture flatness |
The practical rule: a tolerance tighter than the method needs is a cost you pay for nothing. A ±0.003 mm (milling) / ±0.002 mm (turning) callout on a feature that mates with 0.1 mm of clearance buys inspection risk, not function.
How the tolerance is actually verified
A number on a drawing is a claim until it is measured. Verification here runs on a temperature-stable bench with Hexagon CMMs, vision systems, and surface-roughness testers, and the result is documented rather than assumed. For production characteristics the relevant figure is Cpk — a measure of how centred and consistent the process is, not just whether one part passed. Key characteristics are held to Ppk ≥ 1.67 initial, general characteristics to ≥ 1.33; that is the difference between "this part measured in" and "this process is in control".
What this means for you is simple: ask for the inspection evidence, not the assurance. A first-article report (FAIR) and a dimensional layout are documents someone has to produce, and whether they are included changes both the cost and what you actually receive.
When to call for a tight tolerance, and when not to
The most expensive mistake is specifying a tolerance tighter than the function needs, because every tightening step adds a slower cut, a finer tool, a re-cut, and a measurement. Use this checklist before you commit a number to the drawing.
- Mark only mating and sealing features as critical. Everything else should carry a looser general tolerance (for example ISO 2768-m). The fewer tight callouts, the cheaper and the more reliable the part.
- Match the tolerance to the assembly. If the gap is 0.2 mm, a ±0.003 mm (milling) / ±0.002 mm (turning) dimension does nothing a ±0.05 mm dimension would not, and it costs more to prove.
- State the GD&T standard. ISO and ASME Y14.5 can read the same symbol differently; name the one you mean so the tolerance is interpreted, not guessed.
- Keep criticals close to a datum. A tight tolerance on a feature three setups away from its datum is paying twice for the same accuracy.
- Ask what it costs to hold. A competent shop will tell you which dimension is driving the price, that is the one to challenge, not the headline ±0.003 mm (milling) / ±0.002 mm (turning).
What actually drives the cost of a tight tolerance
Three things move the cost when a tolerance tightens: the cut gets slower (finer feeds, lighter passes), the tool gets shorter and stiffer (more tool changes, more setups), and the measurement gets heavier (every critical is a CMM touch, not a caliper check). On a prototype the measurement dominates; on a production run the slower cut does. That is why a per-part price without a quantity and a tolerance class is not a price.
The driver buyers most often underestimate is inspection. A drawing that calls out twenty critical dimensions has a different inspection cost from one that calls out five, and the first-article report is a document someone has to produce.
What do the certificates actually cover?
Three certificates, each with a number you can check with the registrar:
| Standard | Certificate number | Scope note |
|---|---|---|
| ISO 9001:2015 | 116024/A/0001/UK/En | Quality management system |
| IATF 16949:2016 | 131941/A/0001/SM/En | Automotive QMS, excludes clause 8.3 product design |
| ISO 14001:2015 | 116024/B/0001/UK/En | Environmental management system |
The IATF 16949 certificate excludes clause 8.3 (product design). That is normal for a build-to-print manufacturer and it is stated here rather than left for an auditor to discover: we manufacture against your design, it does not originate the design.
How to verify a 3 axis CNC machining supplier
These four checks cost nothing and can be run before any commitment.
- Can they name the registration number? Ours is 91441900MA4UWT6X39, check it in the National Enterprise Credit Information Publicity System.
- Do they name machine families and counts? A manufacturer lists models; a reseller recycles stock photos.
- Are the certificate numbers verifiable? Real ISO/IATF certificates carry numbers you can confirm with the registrar.
- Can you walk the floor? On-site and video audits are welcome at the Dongguan address.
How much of the floor is in this family?
Total machine count is not the question. The question is how many machines sit in the family that makes your part, because that is the queue your part waits in. The floor runs a floor of 100-plus machines: 50+ three-axis centres for prismatic work, 20+ four-axis, 20+ five-axis, 25+ turning and mill-turn centres, Swiss-type lathes for long slender parts, precision grinding and wire EDM for the tightest features.
Having several machines in that family is what lets a part move to another lane rather than sit in a queue when a machine is pulled for service. That, not the headline machine, is what protects a delivery date on a tight-tolerance job.
How does the process actually run, step by step?
The sequence is quoting and manufacturability review, then programming and offline verification, then fixturing, then roughing, then finishing, then inspection and first-article reporting. Each stage has a way to fail, and the expensive ones are the first and the last.
The manufacturability review is where cost and tolerance are actually decided. A pocket depth reduced by a few millimetres, or an internal corner radius opened from 1 mm to 3 mm, can cut cycle time and improve held tolerance more than any change of machine, because it changes the tool that can be used, and a stiffer tool removes more material per minute and drifts less.
Which entity is responsible for the work?
Legally this is Dongguan Zhuohang Ltd, established 2005, Social Credit Code 91441900MA4UWT6X39, operating under the name Zhuohang Precision Machining Factory from No. 8, Shuibian Songyuan Road, Hengli Town, Dongguan, Guangdong, China 523470.
The 18-character code, checked against the National Enterprise Credit Information Publicity System, confirms a real manufacturer. A trading company may hold a business licence as well, but its scope is trading, not manufacturing, and its address is an office rather than a plant.
What this shop actually runs
Capability evidence should come as specifics, not slogans. Behind this guide is a 6,800 m2 plant in Dongguan, China running 100+ CNC machines with 100+ staff. The machine list by category:
- 5-axis machining centres (10+) - Mazak VARIAXIS I-600 (510/910/510 mm travel, 12,000 rpm, 22 kW, 71.6 N·m, 30-tool BT40) and Mazak INTEGREX I-250H S (B-axis 0.0001°, 24 kW, 124 N·m, 38-tool HSK-A63). Cut on compound-angle parts, single-setup multi-face prismatic work, and aerospace fittings where datum transfer loss is unacceptable.
- 3-axis / 4-axis machining centres (50+) - Brother SPEEDIO S500Z2N / S700Z2N (10,000 rpm, 14/21-tool ATC, 0.7 s tool-to-tool, Z-axis 2.2 G) and Mazak VCE-430A L / VCE-570C L (10,000 rpm, 118 N·m, 24-tool ATC). Cut on prismatic parts, plates, brackets, housings.
- Swiss-type turning centres (10+) - Citizen Cincom A20-3F7 (Φ20 mm, 10,000 rpm), TSUGAMI B0206-III / B0205-III (Φ20 mm, 0.1 µm), STAR SR-32JII / SR-32J Type N (Φ32 mm, 8,000 rpm). Cut on long, slender rotational parts at ±0.002 mm.
- CNC turning centres (20+) - HEADMAN T70M/1250 (720 mm swing, 117 mm bore, 3,000 rpm, BMT75 12-station turret). Cut on shafts, bushings, flanges up to ±0.002 mm.
- Wire EDM (5+) - Sodick AQ535L (550/350/300 mm travel, ±20° taper, 800 kg workpiece). Cut on hardened tool steel, internal splines, sharp internal corners that milling cannot reach.
- Inspection: Hexagon CMM + 20+ gauges - Hexagon CMM for coordinate measurement, plus vision system, profilometer, hardness tester, coating thickness gauge, XRF for material verification. The 10:1 rule (gauge 10x more accurate than the band) is applied to every feature.
- Machine highlights - VARIAXIS I-600: one-setup multi-face 5-axis + MAZA-CHECK auto-calibration; INTEGREX I-250H S: DONE-IN-ONE mill-turn, B-axis 0.0001° + Ai thermal shield; SPEEDIO S500Z2N / S700Z2N: Z-axis 2.2 G + 0.7 s ATC; Swiss-type: guide-bush switchable + 0.1 µm resolution.
Tolerance: ±0.003 mm CNC milling / ±0.002 mm CNC turning / ±0.002 mm grinding and wire EDM. Capability: Ppk >= 1.67 initial on key characteristics, Cpk >= 1.33 ongoing.
Certificates: ISO 9001:2015 (116024/A/0001/UK/En), IATF 16949:2016 (131941/A/0001/SM/En, with design clause 8.3 excluded, stated openly) and ISO 14001:2015 (116024/B/0001/UK/En), issued to Dongguan Zhuohang Ltd, registration 91441900MA4UWT6X39, founded 2005.
Where we ship: Austria, Belgium, the Czech Republic, Denmark, France, Germany, Greece, Hungary, Ireland, Italy, the Netherlands, Spain, Sweden and the United Kingdom in Europe; Brazil, Canada, Mexico and the United States in the Americas; China, Israel, Japan, Singapore and Sri Lanka in Asia; Australia and New Zealand in Oceania; and South Africa in Africa — plus other countries and regions worldwide, shipped from our base in Dongguan, China.
Contact: Felipe Iglesias, [email protected], +86 13126536955.
Send the drawing and get the tolerance answered per feature
Contact Felipe Iglesias at [email protected] or +86 13126536955. We will tell you which dimension is driving the number, not just the number.
Frequently Asked Questions
Is inspection documentation included in the quote?
It should be stated explicitly. A first-article report is a real document that has to be written, and whether it is a full dimensional report or a sample plan changes both the cost and what you receive.
How are parts packed for export?
Packing is chosen per part — finished faces bagged and boxed, steel corrosion-protected. Include it in the quote, since it changes the cost and how the parts arrive.
How long does 3 axis cnc machining take?
Lead time is driven less by cutting time than by queue position, fixture design, and inspection. A part that needs a purpose-built fixture has a longer first-article lead and a much shorter repeat lead, which is worth asking about separately.
Can I audit the factory before placing an order?
Yes — on-site and video audits are both welcome at No. 8, Shuibian Songyuan Road, Hengli Town, Dongguan, Guangdong, China 523470.
Which markets do you export to?
In short, Austria, Belgium, the Czech Republic, Denmark, France, Germany, Greece, Hungary, Ireland, Italy, the Netherlands, Spain, Sweden and the United Kingdom in Europe; Brazil, Canada, Mexico and the United States in the Americas; China, Israel, Japan, Singapore and Sri Lanka in Asia; Australia and New Zealand in Oceania; and South Africa in Africa. Our service area also spans Europe, the Americas, Asia, Oceania and Africa — based in China, we serve customers worldwide.
What happens if the first article does not conform?
In short, The nonconformance is documented and the corrective action is agreed before any further parts are made. Whether the replacement cost sits with the plant or the customer depends on where the deviation came from, which is why the revision and the drawing standard are confirmed in writing at the start.
What is the difference between a prototype build and a production build here?
Usually only quantity and scheduling. Both run on the same machines and the same process, which is what makes a later ramp a scheduling change rather than a re-qualification.
Continue reading: What Is 3 Axis CNC Machining · 4 Axis CNC Machining
Standards referenced on this page
- ASTM A582/A582M-12 — Standard Specification for Free-Machining Stainless Steel Bars
- ASTM B211/B211M-19 — Standard Specification for Aluminum-Alloy Rolled or Cold Finished Bar, Rod, and Wire
- ISO 14001 — Environmental management systems — Requirements with guidance for use