1. RFQ checklist — send this, get a usable quote
A quote is only as good as the brief behind it. Before you contact a shop, assemble:
- A CAD model in STEP or IGES (not a PDF or a screenshot — a model is the only thing a shop can program from).
- Material and grade — "6061-T6" or "304 stainless", not just "aluminum". Grade drives machinability, cost and finish.
- Quantities and annual volume — prototype, pilot, or production; the answer changes the process and the price.
- Tolerances only where functional — over-tolerancing every dimension is the fastest way to inflate a quote.
- Surface-finish needs — visible-face requirement, anodize, bead blast, passivation.
- Threads, bores, and any post-processing, and whether a treatment applies before or after coating.
2. DFM checklist — design so it machines cheaply
Design-for-manufacturing is where most cost is won or lost, long before the RFQ:
- Wall thickness at or above ~0.8 mm (more where structural); thin walls chatter and warp.
- Hole depth under ~4:1 depth-to-diameter; beyond that, special deep-drill tooling is slow and risky.
- Internal corners leave a radius (a rotating end mill always leaves one); never design a sharp corner.
- Thread engagement ~1.5–2× the diameter; more buys almost no strength.
- Reach — confirm every critical feature is reachable from one side, or with a simple flip, before adding a 4th or 5th axis.
3. Tolerance & surface-finish guide
| Callout | Typical value | When to specify |
|---|---|---|
| Milled / turned tolerance | ±0.003 mm (milling) / ±0.002 mm (turning) (±0.0002 in) | Critical, functional dimensions on capable equipment |
| Ground tolerance | ±0.002 mm | When fit or geometry demands it |
| As-machined finish | Ra 3.2 µm | Non-visible, functional surfaces |
| Smooth milled finish | Ra 1.6 µm | Visible or sealing surfaces |
| Ground / polished | Ra 0.8 / 0.4 µm | Sealing, sliding or cosmetic-critical |
Reference ISO 2768-m on a drawing to set a default band for un-dimensioned features, so you only pay tight tolerances where they matter.
4. Material quick-reference
| Material | Machinability | Typical use |
|---|---|---|
| Aluminum (6061, 7075) | Excellent | Frames, enclosures, prototypes |
| Stainless (303, 304, 316, 17-4PH) | 303 free-cutting; 304/316 slower | Medical, food, marine |
| Steel (1018, 4140) | Good | Shafts, jigs, wear parts |
| Brass / copper | Excellent | Electrical, thermal parts |
| Titanium (Ti-6Al-4V) | Difficult | Aerospace, implants |
| PEEK / Delrin (POM) | Easy but soft | Insulators, wear pads |
5. Glossary
- First article — a sample machined and measured before the run is released; it proves the program.
- Cpk / Ppk — process-capability indices; Cpk ≥ 1.33 in production, Ppk ≥ 1.67 at initial capability for key characteristics.
- Setup — one clamping of the part; each extra setup adds time and a datum error.
- DFM review — a shop's check of your drawing for manufacturability before quoting.
Frequently updated articles
Deep-dive buyer guides published for CNC Machining China:
- CNC Machining China Factory | CNC Machining China
- CNC Machining China Parts Manufacturer | CNC Machining China
- Quality Assurance at CNC Machining China
- CNC Machining China Services | CNC Machining China
Where to go next
For the service overview, see the services page; for quality evidence, the quality page; for direct questions, contact the team.
What this shop actually runs
A buyer asking for capability evidence should get a specific answer. The facility behind this guide operates 100+ CNC machines across a 6,800 m2 plant in Dongguan, China, 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). The work covers 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). The work covers 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). The work covers 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). The work covers shafts, bushings, flanges up to ±0.002 mm.
- Wire EDM (5+) - Sodick AQ535L (550/350/300 mm travel, ±20° taper, 800 kg workpiece). The work covers 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 held: ±0.003 mm on CNC milling, ±0.002 mm on CNC turning, ±0.002 mm on precision grinding and wire EDM. Capability indices: Ppk >= 1.67 initial on key characteristics; 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 - disclosed openly), ISO 14001:2015 (116024/B/0001/UK/En). Certificates are issued to Dongguan Zhuohang Ltd (USCC 91441900MA4UWT6X39, established 2005).
Service area: 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. Based in China, serving customers worldwide.
Contact: Felipe Iglesias, [email protected], +86 13126536955.
What tolerance should I specify on my parts?
±0.003 mm on milling, ±0.002 mm on turning, and ±0.002 mm on precision grinding and wire EDM — put the number on the feature, not in the drawing title block.
What should I send for a quote?
A 3D model plus a 2D drawing with GD&T, the material, prototype and production quantities, surface finish, and which features are critical. You get DFM notes and an itemised quote.
What is your minimum order?
One part. Prototypes run on the same machines as production, so MOQ 1 is real, not a loss-leader.
Where do you ship?
In short, We ship to 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.
Ready to price your part? Send the drawing and ask for a quotation that names the setups, the machining and finishing windows, and the exchange dates. Contact the team to plan the job.
Continue reading: CNC Machining China Factory · CNC Machining China Services · CNC Machining China
Standards referenced on this page
- ASTM A276/A276M-17 — Standard Specification for Stainless Steel Bars and Shapes
- ASTM B211/B211M-19 — Standard Specification for Aluminum-Alloy Rolled or Cold Finished Bar, Rod, and Wire
- ISO 9001 — Quality management systems — Requirements