CNC manufacturing in China, end to end: processes, tolerances and cost

Complete Guide · CNC Machining CNC manufacturing in China, end to end: processes, tolerances and cost CNC manufacturing in China is the fastest way to turn a CAD file into a precise metal or plastic part — no tooling, no minimum order, days not months. Whether you call it CNC machining or CNC manufacturing, this guide explains the processes, what a 0.002 mm tolerance actually means, what drives cost, and how to buy it in China without the usual guessing. Request a quoteStart with the processes What CNC machining actually is CNC machining is subtractive manufacturing: a computer-controlled tool removes material from a solid block until only your part remains. Buyers search for it as both "CNC machining China" and "CNC manufacturing China" — they are the same thing. Because there is no mold or die to make first, you can get one part or a thousand with the same setup — which is why it is the default for prototypes, low-to-medium volume, and any part whose geometry will still change. Five processes make up almost all machined parts, and each is good at a different shape: ProcessBest forTolerance we hold CNC millingPrismatic parts, pockets, holes, flat faces, enclosures0.005 mm CNC turningRound parts, shafts, bushings, threads0.005 mm Swiss-type turningSmall, long, high-precision turned parts0.005 mm CNC grindingBearing journals, sealing faces, tight-surface finishes0.002 mm Wire EDMHardened steel, sharp internal corners, fine slots0.002 mm Most products combine several. An enclosure is milled, its standoffs are tapped, its mating shaft is turned, and a hardened die detail is wire-cut. A partner that runs all five under one roof — as we do across 80+ machines — removes the handoff risk between shops. See our full capability list. The five processes, compared in depth The table above is the map; here is the terrain. Each process earns its place on a specific kind of feature, and a sourcing decision is usually a question of which process — or which combination — a shop can run under one roof without handing your part to a third party. CNC milling: the workhorse for prismatic parts Milling removes material with a rotating cutter moving over a fixed workpiece, so it owns flat faces, pockets, bosses, holes and any feature with a corner. Because the cutter spins and the part stays put, milling is the natural home for enclosures, brackets, plates and housings — anything whose geometry is built from flat or stepped surfaces. The practical limit is reach: a feature the cutter cannot physically get to from the top or side of the part needs a re-fixture or a rotary axis. The floor that runs this is broad — 50+ 3-axis, 20+ 4-axis and 20+ 5-axis machines, from high-speed Brother SPEEDIO centers (BT30, up to 27,000 rpm, tool change in 0.7 seconds) to the heavier Mazak VCE verticals for larger steel workpieces. A high-speed 30-taper machine is the right tool for aluminum and small parts; a 40-taper machine is the right tool when the cutter has to bury itself in steel or the part is too heavy for a speed center's table. Matching the machine to the material is part of what keeps a quote honest. CNC turning and Swiss-type: round parts done right Turning spins the workpiece against a fixed tool, so it owns anything round — shafts, pins, bushings, spacers, and any feature of revolution. Where milling fights to make a clean cylinder, turning makes it in a single pass. The distinction that matters to a buyer is the one between a standard lathe and a Swiss-type machine. A Swiss-type (sliding-headstock) machine feeds the bar through a guide bushing and cuts close to that support, which is why it holds tight tolerances on long, slender parts that would flex and chatter on a conventional lathe. If your part is a thin shaft with a length-to-diameter ratio of five or more, Swiss is usually the answer, not a preference. Our turning side runs 25+ machines, and the turn-mill side goes further: Mazak QT-COMPACT dual-spindle centers and Brother M-series turret machines turn and mill in one clamping, so a round part with a cross-hole, a flat or a hex comes off complete instead of going through a second operation. For bar-fed small parts, the Citizen, Tsugami and Star Swiss machines hold the fine work. CNC grinding: where the finish spec lives Grinding removes material with an abrasive wheel and earns its place on two features: bearing journals and sealing faces, where the dimension and the surface finish have to be right in the same operation. A ground surface holds a tolerance and a roughness that a milled or turned surface will not, which is why the drawing says “grind” on a shaft seat or a seal face. The cost is speed — grinding is slow — so it belongs on the few features that justify it, not on a whole part. We run 7+ grinders across surface, centerless and cylindrical work, holding ±0.002 mm where the spec calls for it. Wire EDM: sharp corners and hardened steel Wire EDM cuts with a thin, electrically charged wire that erodes the material, so it is not limited by cutter geometry the way milling is. That is why it is the answer for an internal corner that must be truly sharp, a fine slot, or a part that is already hardened — a wire can cut a block at 60 HRC that would destroy an end mill. The wire runs through a start hole and follows a controlled path, so the feature has to be a through-feature or a profile. Wire EDM holds ±0.002 mm, but it is the slowest process here, so it is reserved for the features that cannot be milled or ground any other way. Turn-mill and mill-turn: doing it in one clamp The most useful machines on a modern floor blur the line between turning and milling. A turn-mill center like the Mazak INTEGREX series tilts the tool and indexes the part so a single clamping can turn a diameter, drill a bolt circle and mill a pocket — removing the tolerance loss and the handling time of moving a part between machines. A 5-axis mill like the Mazak VARIAXIS does the mirror of that for prismatic parts, reaching five faces in one setup. The buyer's takeaway is simple: when a part needs both round and flat features, a shop that runs turn-mill removes a handoff you would otherwise pay for twice. How a part goes from file to finish The workflow is the same everywhere, and knowing it tells you where time and cost live: DFM review. Your STEP or IGES model is checked against the machines. Here is where an undercut, an impossibly thin wall, or a threaded hole too close to an edge gets flagged — before metal is cut. CAM programming. The model becomes toolpaths: which cutter, which speed, which approach. Setup and machining. The block is fixtured and cut. Multiple setups mean more time and more chance of misalignment — a 5-axis machine can reach five faces in one setup. Finishing. Deburring, anodizing, plating, brushing, laser marking — the surface treatments that make a part look and perform like a product. Inspection. CMM and XRF verification against the drawing, with a report if your program needs it. The machine floor behind the process Numbers on a website mean nothing unless they map to machines on a floor. Ours sits in Hengli, Dongguan — 6,800 m², 100+ staff, running since 2006 (Zhuohang) — and the equipment list is what the tolerances are derived from, not a marketing ceiling. Milling: 50+ 3-axis, 20+ 4-axis, 20+ 5-axis. High-speed Brother SPEEDIO 30-taper centers for aluminum and small parts; Mazak VCE 40-taper verticals for heavier steel and workpieces up to 1,300 × 700 × 600 mm. Turning: 25+ machines. Mazak QT-COMPACT dual-spindle mill-turn centers for done-in-one parts, plus Citizen, Tsugami and Star Swiss-type machines for long, slender bar-fed work up to ø32 mm. Turning handles workpieces up to ø720 × 1,280 mm. Grinding: 7+ machines across surface, centerless and cylindrical work for bearing journals and sealing faces. Wire EDM for hardened steel and sharp internal corners. The rated capability of the line is ±0.005 mm on milling and turning and ±0.002 mm on grinding and wire EDM. The support equipment matters as much as the spindles: laser marking, two blast cabinets, an ultrasonic cleaning line, passivation, polishing, tumbling, and two hot-air ovens rated to 500°C for low-temperature stress relief and aging. Heat treatment above that — titanium stress relief runs around 788°C, for example — goes to a qualified outside partner, and the lead time reflects it. A buyer should ask any shop one question here: which of these steps leave the building, and what does that do to your week. Tolerances: what the numbers really mean Tolerance is how much a dimension may vary and still be acceptable. A drawing that says “10.000 mm ±0.003 mm” means the part may measure between 9.997 and 10.005 mm. The tighter the tolerance, the more a shop must control its tools, temperature and process — and the more it costs. Our published numbers — 0.005 mm for milling and turning, 0.002 mm for grinding and wire EDM — are what the line can hold reliably, not a marketing ceiling. To put 0.003 mm in perspective: it is about one-thirtieth the thickness of a human hair. FeatureStandard toleranceTight tolerance Linear dimension±0.05 mm±0.01 mm Bore / hole diameter±0.05 mm±0.005 mm Flatness / parallelism0.05 mm0.01 mm Surface finishRa 3.2 µmRa 0.4 µm Here is the rule that saves buyers the most money: only tolerance what has to be toleranced. A drawing covered in ±0.005 mm callouts will be quoted high because every one of those digits has to be verified. Tolerances belong on the features that mate, seal, or locate; everything else can be general. Tolerance, precision and repeatability — three different things Buyers use these words interchangeably, but they measure different risks: Accuracy — how close a part comes to the true dimension. Precision (repeatability) — how close one part comes to the next. You can be repeatable but wrong, or right on average but scattered. Tolerance — the band you accept, which you choose in the drawing. When you qualify a shop, you care about both accuracy and repeatability: the first part has to be right, and the ten-thousandth part has to match the first. That is what our CMM verification checks, and why we publish the numbers instead of promising “high precision” with no digits attached. How SPC proves the process, not just the part A single measured part proves one part. What a sourcing manager actually needs to know is whether the next ten thousand parts will match it — and that question is answered by statistical process control, not by a certificate. SPC watches a dimension over time and turns it into a number that tells you whether the process is stable and centered. Two numbers carry the meaning. Cp measures how wide the process spread is relative to the tolerance band — whether the machine could hold the spec at all. Cpk measures both the spread and where it sits — whether the process is centered and stays inside the band with margin. A process can have a high Cp and a poor Cpk if it is consistent but off-center, which is exactly the failure that looking only at averages misses. Our standard is the automotive one: Cpk ≥ 1.67 on critical characteristics and Cpk ≥ 1.33 on general characteristics. Those are the gates a dimension has to clear before a run is released, and they are the difference between “the first part measured right” and “the process is in control.” Reading a real control chart, line by line The best way to understand this is to read an actual chart. Here is a real one from a production part: the process sits well inside the spec on both sides, which clears the 1.67 critical-characteristic gate with room to spare. The verdict on that chart was “OK,” and the reason matters: it is not that one part measured right. It is that 100 sampled parts, tracked over time, stayed centered and stable — which is the only evidence that predicts part 10,001. When you qualify a shop, ask to see a chart like this for a dimension that matters to you, not a single golden sample. GD&T, without the jargon Geometric Dimensioning and Tolerancing (GD&T, per ASME Y14.5) is a language for specifying not just how big a feature is, but how it must relate to others: flatness, position, perpendicularity, runout. It matters because two parts can both meet their individual ±0.05 mm callouts and still not fit together, if their features are oriented wrong. For most commercial parts, simple linear tolerances are enough. GD&T earns its keep on mating parts, rotating assemblies and anything with a functional datum — and a shop that reads a GD&T frame without flinching is a shop that has done real work. Inspection: what proves the dimension For a quality lead. Machining and inspection are two halves of the same promise, and the instruments a shop owns tell you whether it can prove what it claims. The core of ours is a Hexagon CMM (coordinate measuring machine) that measures geometry to the drawing; around it sit vision measuring machines, a surface-roughness and contour machine, a gear measuring center, a laser microscope for surface texture, hardness testers, a coating-thickness gauge, and an XRF analyzer for alloy confirmation. Each instrument answers a different question: CMM — does the geometry match the drawing, feature to feature and datum to datum? XRF / PMI — is this actually the alloy the mill certificate says it is? Material mix-ups happen, and a hand-held spectrometer catches them before the part ships. Surface-roughness and contour machines — does the finish hit the Ra you specified on the sealing face? Hardness and coating-thickness gauges — did the heat treatment and plating land where the spec says? Salt-spray and tensile testers — for programs that call out corrosion or strength verification. The point for a buyer is the same one made earlier: ask which instrument verifies your part and whether the report travels with it. A first-article report (FAI) ties a specific serialized part to the drawing, dimension by dimension, and a shop that will send one on request is a shop that is not afraid of its own numbers. Materials: the first decision, not an afterthought Material drives strength, weight, corrosion, thermal behavior, finish and cost — often more than the machining itself. The short map: Aluminum (6061, 7075) — the default: light, strong enough, machines fast, anodizes well. Grade guide. Stainless (303, 304, 316, 17-4PH) — corrosion and strength, at a machining-time premium. Grade guide. Titanium (Gr2, Gr5) — best strength-to-weight and biocompatibility, slowest to cut. When it is worth it. Brass and copper (C360, C110) — conductivity and machinability. Grade guide. Magnesium (AZ31B) — the lightest structural metal, with a fire-safety question to ask. Grade guide. Engineering plastics (POM, nylon, PEEK) — where weight, cost or electrical isolation wins. Plastics guide. The full selection logic lives in the materials selection guide; here the point is that material and process are chosen together, because a metal that is cheap to buy can be expensive to cut. Machinability: the hidden cost inside every material For a manufacturing engineer. Material choice is a machining-cost decision as much as a performance decision, because metals do not all cut at the same speed. Machinability is usually indexed against a reference steel — a rating of 100% means it cuts at the baseline rate, higher is faster, lower is slower and harder on tooling. The practical ranking for the common grades: Aluminum (6061) — among the fastest to machine; cheap to buy, cheap to cut, anodizes cleanly. The default for a reason. Brass (C360 free-machining) — fast and self-lubricating at the cut; the go-to for fittings and electrical parts. Steel (12L14, 1215 free-machining) — cuts well; the standard stainless grades (303, 304, 316) are noticeably slower because they work-harden at the edge. Titanium (Gr5) — the slowest and most expensive to cut on this list: low thermal conductivity keeps heat at the tool, and the material springs back off the cutter. Engineering plastics (POM, PEEK) — fast to machine, but they move after cutting, so tight tolerances need a stress-relief strategy. The consequence is a rule of thumb worth internalizing: a cheap-to-buy material can be the expensive one to machine, and the reverse. 7075 aluminum costs more per kilo than 6061 and is gummier to cut, but its strength can remove an entire part from the assembly. Stainless costs more to machine than aluminum, but a stainless part may need no coating where an aluminum one needs anodize. Choose the material and the process together, and the quote stops surprising you. The full selection logic is in the materials selection guide. 3-axis vs 5-axis, and when it matters A 3-axis mill moves the cutter in X, Y and Z. A 5-axis machine adds two rotary axes, so the part (or the cutter) tilts. The payoff is real but specific: fewer setups (reaching five faces in one hold), tighter feature-to-feature accuracy (no re-fixturing error), and undercut and complex geometry that 3-axis cannot reach at all. The cost is higher machine time. The decision is economic: complex or setup-sensitive parts justify 5-axis; simple prismatic parts do not. The full comparison. Machine geometry and the setup count The axis count is really a proxy for one thing: how many times a part has to be taken out of a fixture and put back. Every re-fixture adds handling time and — more expensively — re-introduces a locating error into the tolerance budget. That is the whole story behind the 3-axis-versus-5-axis question, and there are three useful stops along the way. 3-axis: two and a half sides per setup A 3-axis machine reaches the top face and, with side access, some of the sides — but a part that needs features on all six faces will be flipped several times. For a simple bracket or plate this is fine and cheap; for a part with a bore that must be concentric to a face on the opposite side, every flip is a risk. 4-axis indexing: rotation without the cost of full 5-axis A 4th axis is usually a rotary indexer that rotates the part to a fixed angle so the mill can reach another face precisely. It is the economical middle ground for parts that need features at 90° or 180° intervals — a housing with holes on four faces, for example. You get the accuracy of a controlled rotation without the machine rate of a simultaneous 5-axis center. 5-axis: five faces, one clamp A true 5-axis machine tilts and rotates the part or the cutter continuously, so the tool can stay short and rigid and the part stays in one clamp. The wins are the three already named — fewer setups, tighter feature-to-feature accuracy, and geometry a 3-axis cannot reach at all, like an angled pocket or an undercut. The cost is machine time. The decision rule has not changed: if the part is setup-sensitive or geometrically complex, 5-axis earns its rate; if it is a flat plate, a 3-axis machine is the cheaper honest answer. The full 5-axis comparison. What actually drives CNC cost For a sourcing engineer. Five levers, in rough order of impact: Material. Titanium and stainless cost more than aluminum per part because they cut slower and wear tools. Geometry. Deep pockets, thin walls, and small internal radii need long, delicate toolpaths and more scrap risk. Tolerance. Every tight digit adds inspection time. Tighten only what must be tight. Quantity. Setup and programming are one-time; spreading them over more parts drops unit cost steeply, which is why a no-MOQ shop that also scales is the sweet spot. Finish. Type III hard anodizing, plating and mirror polishing add process steps and cost. A useful quote separates these so you can see where the money goes — and usually shows you the one design change that would cut the most cost. That is the point of a real DFM note. Design for manufacturing, explained. Cost drivers, one level deeper The five levers above set the shape of any quote; here is where each one actually moves the number. Setup and programming amortize over volume Programming and fixturing are one-time costs that hit the first part hard and the thousandth part barely at all. A quote at 10 pieces is dominated by setup; the same part at 10,000 pieces is dominated by raw material and machine time. This is why a no-MOQ shop that also scales is the sweet spot: you pay setup once at prototype volume, and the unit price falls as quantity climbs without a tooling bill in between. Tooling and tool wear Cutters wear, and some materials eat them faster than others. Titanium and hardened steel consume tools at a rate aluminum never will, and that cost lands in the part price. Deep features also cost tooling because they force long, slender cutters that run slow and break more often. The design-side fix — realistic corner radii, shallow pockets, standard threads — is the same list DFM always gives. Finishing and post-processing Every finish step is a second process with its own handling, inspection and lead time. Type III hard anodizing, nickel or chrome plating, passivation and mirror polishing each add a step and a queue. A finish that leaves the building — outsourced plating or heat treatment — adds transit time on top of process time, which is the quietest schedule risk in a quote. The honest quote separates all of this so you can see the money move. DFM, explained. Lead time, realistically A simple aluminum part can ship in days; a hard-anodized, tight-tolerance titanium assembly takes longer. The schedule is set by three things: material availability, machine and finishing capacity, and the number of setups. The honest answer is always “it depends on the drawing” — a shop that quotes a flat lead time before seeing the model is guessing. Send the model, get a real number. Lead time tiers, and what sets them We publish three bands because lead time is set by the drawing, not the calendar: about 3 days for a simple part with available material and a short process, about 7 days for standard work, and up to 30 days for complex parts whose process runs ten to twenty steps or that need outsourced surface treatment or heat treatment. The driver is the number of process steps — more operations, more setups, more finishes, more queue — not the machine time itself, which is usually the smallest slice. A part that needs a finish the shop does not run in-house picks up transit on both ends, and that is often the difference between a 7-day and a 30-day part. The only honest answer before seeing the model is “it depends”; the honest answer after seeing it is a date. Quality: how you know the part is right A dimension is only as good as the proof behind it. We verify with CMM (coordinate measurement) for geometry, XRF for alloy against the mill certificate, and a first-article report (FAI) when your program requires it. Ask any shop two questions: “what instruments do you verify with?” and “will you send the report?” A shop that hesitates on either is not controlling its process. Our instruments and certifications. Certifications, and what they actually mean A certificate is a statement about a quality system, not a guarantee about a specific part — but the right ones tell you a shop has been audited against a standard it cannot fake its way through. Ours, all registered through URS: ISO 9001:2015 (certificate 116024/A/0001/UK/En, valid to 2027) — the baseline quality-management standard, scoped to machining of metal parts. IATF 16949:2016 (certificate 131941/A/0001/SM/En, valid to 2027) — the automotive quality standard, and the one that matters most for a buyer shipping into an automotive supply chain. Read the scope carefully: it covers manufacture of CNC metal parts excluding product design under clause 8.3. In plain terms, we manufacture to your design and do not claim design responsibility — an honest limitation, and one a buyer should read into any IATF certificate the same way. ISO 14001:2015 (certificate 116024/B/0001/UK/En, valid to 2027) — environmental management, which matters when your customer asks about your supplier's footprint. The buyer's habit here is to ask for the certificate number and check the scope, not just the logo. A logo is a jpeg; a number and a scope you can verify are a claim. On the floor the checks are concrete rather than aspirational. Every BOM line is cross-checked against the drawing and the purchase spec before release, so a 6061 callout cannot silently become 5052. Critical alloys are bought through a cross-checked second source with a matching mill test certificate, and each incoming lot is confirmed by XRF / PMI before it reaches a machine. For aerospace programs we run FAI per AS9102 so the first article is dimensionally signed off before the run begins. CNC in China vs elsewhere China is the world’s largest machining base for a reason that is structural, not just cheap: the supply chain around it — raw material, tooling, surface treatment, and the electronics that go inside the enclosure — all sit within hours of each other. That density shortens lead time and reduces the hidden costs of coordinating five vendors across five time zones. The trade-offs are the ones covered honestly in this comparison: tariffs and logistics versus supply-chain depth. For precision metal and prototypes, China remains the default; for bulky, low-value or tariff-sensitive volume, final assembly is increasingly moving closer to the end market. Tariffs, HS codes and the real landed cost The price of a part out of China is not what it costs at your dock. Between the two sits classification, duty and freight — and a sourcing manager who ignores them is pricing a fiction. This is the short version; the details move with policy, so confirm against current USTR and CBP figures before you commit. Classify it right: HS, HTS and the six-digit root Every traded good carries a harmonized code whose first six digits are the same worldwide; the US then extends it to a ten-digit HTS code for imports. Classification is driven by what the part is and does — its material and function — not by how it was machined. A steel structural part often lands in chapter 73, an aluminum one in chapter 76, a gear or shaft in chapter 84. Get the code wrong and the duty can change by multiples, so the code is a line item in the quote, not an afterthought. The tariff breakdown. The add-on duties: Section 232 and 301 On top of the base rate, US importers of Chinese goods face two country-specific layers. Section 232 applies to steel and aluminum regardless of origin — 25% on steel and 10% on aluminum — so a machined steel or aluminum part carries it automatically. Section 301 applies to China specifically and adds a further percentage on covered codes, historically in the 7.5–25% range. The two stack. A buyer should have the supplier state the proposed HTS code and whether the part hits either list, so the landed cost is known before the PO, not discovered at customs. Incoterms and who owns what The trade terms decide where risk and cost change hands. FOB a Chinese port means the seller covers everything to the vessel and you take over at the rail — the most common and transparent split. EXW puts everything on you from the factory gate. DDP has the seller deliver duty-paid to your door, which is convenient but folds the tariff into the price — and if a forwarder quotes “door-to-door, tax included” below what the real duty would cost, that is a red flag that the value is being under-declared, and the compliance risk lands on the importer of record: you. Duty and landed cost in full. CNC machining vs casting, forging and 3D printing CNC is not the only way to make a metal part, and it is not always the right one. The quick decision map: ProcessBest forTrade-off CNC machiningPrototypes, low–medium volume, tight tolerance, complex geometryUnit cost rises with complexity Die castingHigh-volume aluminum/zinc partsTooling cost and time up front ForgingHigh-strength structural partsLimited geometry, post-machining needed 3D printingOrganic geometry, quick iterationsMaterial and finish limits; slower at volume For most hardware startups and low-to-medium volume, CNC is the default because there is no tooling and no minimum — you pay only for the part. At very high volume, casting or forging can undercut CNC on unit cost, but you buy that with a tool and a lead time. A partner that runs CNC and also sources casting and stamping through qualified partners can advise you when the crossover arrives, rather than selling you their one machine. Our full process range. Reading a quote, line by line A useful machining quote separates four things, and a vague one hides them. When you receive a number, look for: Material cost — the raw stock, separated from machining. Machining cost — machine time and setup, which is where geometry and tolerance show up. Finishing — anodizing, plating, or any surface treatment, called out explicitly. NRE — fixtures, programming, or one-time setup that is not amortized into unit price. If the quote is a single number with none of these broken out, you cannot tell where the money is — and you cannot ask for the design change that would cut it. The point of a broken-out quote is that it leads to the DFM conversation. How DFM cuts that number. A supplier-selection checklist Boiled down to what to verify before you send the first PO: CheckWhat you are looking for Machine list and axis countReal equipment that matches your part, not adjectives Published tolerancesNumbers, with the process that holds them Inspection instrumentsCMM, XRF, surface and hardness — and reports on request SPC evidenceA control chart, not a golden sample Certificates with scopesISO 9001, IATF 16949 (read the exclusions), ISO 14001 MOQ and lead-time honestyMOQ of 1, and lead times that respond to the drawing In-house finishingAnodize and plating that do not leave the building DFM pushbackA note, not a blind quote None of these is a trick question; a competent shop answers all eight without blinking. How to choose a machining partner Five tests, same as for any manufacturing partner: They publish tolerances and machine lists. Vague adjectives are a red flag. They push back on the drawing. A shop that quotes blind is guessing about your cost and your risk. They verify, not just claim. CMM and XRF, with reports available. They can do the finish. A part that leaves for outside anodizing picks up a week and a handoff risk. They scale. No-MOQ prototyping that does not choke when you need ten thousand units. Due-diligence questions to ask any shop The five tests above become concrete in a short list of questions. Run these on any candidate, in a call or an email, and watch which ones get answered with specifics and which get answered with marketing: “Which machines make my part, and how many axes do they have?” — a real answer names machines; a vague one says “advanced equipment.” “What tolerance can you hold on this feature, and how do you prove it?” — the answer should be a number plus an instrument. “Can I see a control chart for a dimension like this one?” — SPC evidence is the single strongest signal of a controlled process. “Which of these steps — anodize, plating, heat treatment — happen in your plant?” — every step that leaves adds time and a handoff. “What is the certificate number and scope, not just the logo?” — and read the exclusions. “What HTS code will you use, and does my part hit Section 232 or 301?” — a shop that cannot answer this is not thinking about your landed cost. “Who is my contact, and what do they speak?” — an engineer-to-engineer conversation in your language saves more money than any single design change. A partner answers these fast, with numbers. A vendor stalls. That is the whole test. Frequently asked questions What tolerance can CNC machining hold?A capable shop holds ±0.05 mm routinely and ±0.01 mm or tighter on request. We publish 0.005 mm for milling and turning and 0.002 mm for grinding and wire EDM. The right question is not “how tight can you go” but “how tight does this feature actually need to be” — because every extra digit costs money. How much does CNC machining cost in China?It depends on material, geometry, tolerance, quantity and finish. A simple aluminum part is a few dollars at volume; a tight-tolerance titanium assembly is far more. A good quote separates material, machining, and any NRE, so you can see where the money goes. What is the difference between milling and turning?Milling moves a rotating cutter over a fixed part and suits prismatic shapes; turning rotates the part against a fixed tool and suits round shapes. Many parts need both. The full comparison. What files do you need for a quote?A STEP or IGES model plus a drawing with tolerances, material and finish. A PDF drawing alone is not enough to machine from. Do you machine plastics as well as metal?Yes — engineering polymers including POM, nylon, PC, ABS, PMMA and PEEK, chosen for the same reason as metal: geometry and volume. Can you hold tolerance and still be fast?Tight tolerance and speed trade against each other, but a no-MOQ shop built for NPI can turn a tight part in days, not weeks, because setup and inspection are the bottleneck, not the machine itself. What does Cpk actually tell me as a buyer?It tells you whether the process is centered and stable, not just whether one part measured right. Cpk folds in both the spread and the position of the process against the tolerance band. A shop that reports Cpk ≥ 1.67 on critical dimensions and ≥ 1.33 on general ones is holding a standard you can audit, not a promise. Do I need a certificate of origin, and does it save me duty?For the US, no preferential certificate applies: there is no China–US free-trade agreement, so a general certificate of origin proves origin but does not reduce duty. Chinese parts into the US pay the base rate plus any Section 232 and 301 add-ons that apply to the code. What is the difference between 4-axis and 5-axis?A 4th axis is usually a rotary indexer that rotates the part to a fixed angle so the mill reaches another face; a true 5-axis machine tilts and rotates continuously and reaches five faces in one clamp. For parts with features at set angles, 4-axis is the cheaper correct answer; for angled or contoured geometry, 5-axis earns its rate. How do I know the material is what I ordered?Ask for the mill certificate and for XRF/PMI confirmation at incoming inspection. A hand-held spectrometer checks the alloy against the certificate in seconds and catches a material mix-up before it becomes a shipped part. What does MOQ of 1 actually mean in practice?It means you can order a single prototype with no tooling and no minimum, because there is no mold or die to amortize. The same shop should then scale with you as quantity climbs, so the setup cost you paid once is spread over the run instead of repeated at every order. Sources & further reading ISO 9001:2015 — Quality management systems (ISO) IATF 16949:2016 — Automotive quality management (IATF Global Oversight) ISO 14001:2015 — Environmental management (ISO) ASM Handbook series — metals properties and machining reference (ASM International) MatWeb — material property database Send the model, get a real quoteUpload a STEP/IGES file to [email protected] — you get a price, a lead time, and a DFM note flagging the design changes that cut cost before you commit.Request a quote Related articlesThe Complete Guide to Material SelectionThe Complete Guide to DFMCNC Milling vs Turning