Micro CNC Machining Services

Milling and turning hold ±0.003 mm (milling) / ±0.002 mm (turning) and grinding holds ±0.002 mm, with Ppk ≥ 1.67 at the initial study on key characteristics and ≥ 1.33 on general characteristics. On a representative length characteristic (76.1–76.5 mm), our SPC shows Cpk 1.851 (one characteristic on one part, not a blanket capability claim) — a measured capability, verified on Hexagon CMMs.

Read the tolerance band before you read the index. Cpk is a ratio of the tolerance band to the process spread, not an absolute measure of accuracy. The figure above was recorded on a length characteristic with a 0.4 mm band (76.1–76.5 mm) — wide by design. Hold the same process spread against a ±0.005 mm feature and it fails outright. Ask for the band, the subgroup count and the sampling window on every capability number a supplier quotes.

The two bands exist for different features: ±0.003 mm (milling) / ±0.002 mm (turning) is the workhorse band for housings, journals, and locating features, while ±0.002 mm is reserved for the roundness-critical seats that actually earn it. A feature does not get the tight band by default; it gets the band the drawing assigns, and the process is picked to hold that band.

Process	Held tolerance	Feature it serves
CNC milling	±0.003 mm	Housings, locating faces, hole patterns
CNC turning	±0.002 mm	Journals, pins, bushings
Precision grinding	±0.002 mm	Bearing seats, roundness-critical surfaces

How is a fit verified before it ships?

A fit is two features with one relationship. The CMM measures each mating feature against its datum and confirms the resulting clearance, transition, or interference, so the fit is proven before the parts ship, not discovered at your dock.

The verification reads the pair, not the parts. A bearing seat measured alone can be within tolerance and still not fit its journal, because the clearance is what matters, not the individual sizes. The CMM reports the relationship between the two features against the same datum, so the fit is a measured result rather than a hope.

There is also a timing point: the fit is verified on the finished part, after every secondary operation has had its chance to move metal. A coating can close a clearance, and a heat treatment can shift a bore, so the fit check happens last — on the part the buyer actually receives, not on the blank that left the machine.

How does the DFM review read the GD&T?

The DFM review reads the tolerance zones, not just the dimensions. If a control is ambiguous, missing a datum, or impossible to measure, the engineer flags it before quoting, because a control the CMM cannot verify is a control the shop cannot hold.

That flag is a service, not a delay: it stops a bad drawing from becoming a bad part. The review checks three things in order. First, whether the datum structure is complete enough to measure from. Second, whether the material condition modifiers and tolerance values are achievable on the named process. Third, whether the feature can be machined at all — a sharp internal corner or a thin unsupported wall gets flagged before it gets cut.

you receive the flags in writing, so the drawing is corrected once, on paper, instead of being discovered wrong at inspection.

How does a multi-process part keep its datum reference?

A part that moves from turning to milling to grinding can lose its datum at every hand-off. The service prevents that by planning the sequence so each operation locates the part the way the drawing does, and by verifying the geometric controls on the CMM after the final operation, not after each one in isolation.

Operation sequence	What it must preserve	Verified tolerance
Turning, then milling	Concentricity and position against the datum	±0.003 mm
Milling, then grinding	Roundness and size on the seat	±0.002 mm

A control is only proven on the finished part, after every operation has had its turn at the datum. The CMM reads the final state, which is the only state you receive. The sequence is the mechanism that makes the final state match the drawing.

Which secondary operations preserve the tolerance?

• Surface finishing: standard and hard anodizing, plating, powder coating, painting, brushing, polishing — specified so the finish does not eat the tolerance.
• Heat treatment: vacuum, bright, carburizing, nitriding, stress-relief aging. In-house ovens reach 500 °C; titanium stress relief above that goes to a qualified partner.
• Deburring, tapping, laser marking, assembly: included as the print requires.

Every secondary operation has to respect the tolerance it inherits. An anodize layer adds thickness, so a tight bore is machined with the coating allowance already accounted for. A heat treatment moves metal, so a seat that must hold ±0.002 mm is ground after the furnace, not before it. The planner sequences the secondary operations so the finish lands on the part without erasing the geometry.

The disclosure rule is simple: whatever is outsourced is named, and whatever is named stays accountable. You know which step left the building, which partner handled it, and how the incoming check confirms it did not break the tolerance. A finishing step that is hidden is a hand-off that can quietly lose the datum, which is exactly the failure the GD&T discipline exists to prevent.

What red flags signal a GD&T-weak service?

What should a buyer ask a machining service before sending the drawing?

• Ask whether process planning starts from the datum structure, and whether the DFM review reads the GD&T or only the dimensions.
• Ask which instruments verify the geometric controls, and whether the service measures with a CMM or a caliper.
• Ask for the Cpk chart on a representative characteristic, compared to a Ppk ≥ 1.67 initial-study target for key characteristics.
• Ask how a fit is confirmed before shipping, and whether it is measured against the datum.
• Ask which operations run in-house and which are outsourced, and how each is disclosed.
• Ask how a multi-process part keeps its datum through turning, milling, and grinding.

A service that answers all six in writing is one whose tolerance claim you can verify before the first part ships. The questions cost nothing to ask, and the answers tell you more than any brochure about how the shop will treat your drawing.

What this shop actually runs

If you ask for capability evidence, you deserve a specific answer. This facility operates 100+ CNC machines across 6,800 m2 in Dongguan, China, staffed by 100+ people. The machines, listed 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). Chosen for 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). Chosen for 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). Chosen for 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). Chosen for shafts, bushings, flanges up to ±0.002 mm.
• Wire EDM (5+) - Sodick AQ535L (550/350/300 mm travel, ±20° taper, 800 kg workpiece). Chosen for 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 bands: ±0.003 mm milled, ±0.002 mm turned, ±0.002 mm ground or wire-cut. Capability indices: Ppk >= 1.67 at the initial study; Cpk >= 1.33 ongoing in production.

Certifications: ISO 9001:2015 (116024/A/0001/UK/En) · IATF 16949:2016 (131941/A/0001/SM/En, design clause 8.3 excluded) · ISO 14001:2015 (116024/B/0001/UK/En), held by Dongguan Zhuohang Ltd (USCC 91441900MA4UWT6X39, since 2005).

Service area: we supply 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, with worldwide delivery from China.

Contact: Felipe Iglesias, [email protected], +86 13126536955.

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