CNC Machining: The Complete Guide to Processes, Machines, Materials, Tolerances and Costs

By SHENGHAO Manufacturing Team · Last updated October 16, 2026

If you buy or specify precision metal parts, you already buy CNC machining — and the gap between a good quote and a bad one is usually decided by tolerances, setup count and design choices made long before the first chip flies. This guide walks the whole chain: how the process works, what the machines actually do, which materials to specify, what tolerances are honestly achievable, and where the money in a quote really goes.

It is written for the people who specify and buy those parts: design engineers who need tolerances, materials and design rules; procurement managers who need cost structure, lead times and a way to judge a supplier. If your drawing is already on your desk, the fastest route through this guide is the cost breakdown and the supplier checklist.

What Is CNC Machining?

CNC machining (computer numerical control machining) is a subtractive manufacturing process in which a computer program controls machine tools that remove material from a solid workpiece — typically a block, bar or plate of metal or plastic — until the finished part matches a CAD model. The cutting physics are the same as manual machining. What the computer adds is repeatability: the same program produces the same part on the thousandth run as on the first. Any mill, lathe, grinder or EDM machine becomes a CNC machine the moment a numerical control takes over axis movement.

A short history, because the timeline explains the machine park in any modern shop:

How it relates to other processes. Conventional (manual) machining uses the same tools and chips, but CNC replaces the machinist's hands with a program — which is why it wins on repeatability and complex geometry. 3D printing is additive: it builds a part up layer by layer instead of cutting material away. The two are complements — many shops print a prototype housing, then CNC-machine the mounting faces and bores that must hit a tolerance. Section 8 compares them side by side.

How Does CNC Machining Work?

The CNC machining process runs the same five steps on every job. Understanding them shows where cost and risk sit in a quote.

1. CAD model. The part is designed in CAD (SolidWorks, Fusion 360, NX, CATIA) and exported as a STEP file — the single source of truth for geometry.
2. CAM and G-code. CAM software (Mastercam, hyperMILL, PowerMILL) converts the model into a toolpath; a post-processor turns it into G-code the control understands. G-code moves the axes — G00 rapid traverse, G01 a straight cutting move — while M-code switches auxiliary functions on and off (M03 spindle start, M08 coolant). FANUC, Siemens, Heidenhain and Mitsubishi controls read dialects of the same language.
3. Setup and workholding. The blank is clamped in a vise or fixture and datum-ed — the reference surfaces every dimension is measured from. Setup count is the quiet cost driver: every re-clamp adds hours and a fresh chance for misalignment.
4. Machining operation. The spindle removes material as chips. Milling cuts with a rotating tool on a fixed part; turning rotates the part against a fixed tool. Coolant controls heat, and the program balances cutting speed and feed against tool life.
5. Inspection. The first part is measured against the drawing — often as a first article inspection (FAI) on a ballooned drawing that ties every dimension to a numbered bubble — then production continues with in-process checks and a final dimensional report. A coordinate measuring machine (CMM) does the measuring on anything precision-critical.

Steps 3 and 5 deserve emphasis: the fixture is what makes a ±0.02 mm feature repeatable, and the paperwork is what lets you prove the part meets spec months later. The sequence above is what a complete quality control process and first-article inspection looks like.

Types of CNC Machines

"CNC machine" is a collective term, not one machine. The right platform depends on the part's geometry — and the wrong platform shows up in your quote as extra setups.

Milling: 3-axis, 4-axis, 5-axis

A 3-axis mill moves the tool in X, Y and Z, machining everything reachable from above in one setup: plate parts, brackets, housings, flat pockets. The moment the part needs features on five or six faces, you re-clamp it — and each re-clamp introduces roughly ±0.02–0.05 mm of re-registration error that stacks up across faces.

A 4-axis mill adds a rotary table, so four-sided hole patterns and ring-shaped parts finish in one setup instead of four.

A 5-axis mill adds two rotary axes so the tool can approach the workpiece from almost any angle. Two variants matter commercially: 3+2 positioning holds the part at a fixed angle and cuts with three axes — setups eliminated without the full 5-axis price — while simultaneous 5-axis moves all five axes at once for complex freeform surfaces.

The real value of true 5-axis is not fancy geometry. A multi-sided part never gets re-clamped, so position tolerance across faces stays tight: that is how a five-face housing holds ±0.005 mm on its hole pattern, where the same part on a 3-axis machine with four setups would be lucky to hold ±0.02 mm. Shorter, stiffer tools also mean less vibration and better finish. The trade-off: 5-axis hours cost 1.5–3× a 3-axis hour — a decision, not a default.

Lathes and turning centers

A CNC lathe rotates the workpiece while the tool feeds in. It owns rotational parts: shafts, bushings, nuts, knobs, spacers. A turning center adds a powered turret with driven tools for light milling without leaving the machine.

Mill-turn centers

A mill-turn (turn-mill) center combines both: a valve core that needs a turned body, a milled flat and a cross-drilled hole finishes in one setup instead of four to six, and the single-setup cost often beats multi-setup pricing outright.

Swiss-type lathes

Swiss-type machines feed the bar through a guide bushing that supports it right at the cut. They excel at slender, small-diameter turned parts in volume — pins, screws, watch components, medical fittings — where an ordinary lathe would let the part deflect.

EDM: wire and sinker

Electrical discharge machining erodes metal with controlled sparks. No cutting force means no deflection, and hardness does not matter — both types machine hardened tool steel no cutter can touch. Wire EDM cuts a 2D profile through the material like a very accurate wire saw: punches, slots, tapered parts. Sinker (ram) EDM sinks a shaped electrode into the workpiece for 3D cavities, blind holes and mold textures; each cavity needs its own electrode, which is where the setup cost lives.

Grinding

A grinder removes a thin stock allowance — typically 0.1–0.3 mm — with an abrasive wheel. It is the finishing step for bearing seats, hydraulic spools, guide rails and anything hardened beyond HRC 45, holding ±0.001–0.005 mm at Ra 0.1–0.4 µm. "Grind this feature" in a quote means added days and a higher rate.

Waterjet, plasma and laser

These are cutting processes, not precision finishing. A waterjet cuts cold with abrasive water — no heat-affected zone, good for titanium and thick plate. Plasma melts through thick carbon steel cheaply but leaves a wide heat-affected zone. A laser profiles thin sheet quickly. All three prepare stock ahead of the CNC work.

A shop's machine list is the first hard fact to check when you evaluate a supplier. SHENGHAO, for reference, runs 35+ high-precision CNC machines across 3/4/5-axis with wire EDM and grinding in-house — a multi-sided housing quotes as one setup instead of a relay between vendors. Full capability list: 3, 4 & 5-axis CNC milling and turning.

CNC Machining Materials

Material choice drives cost, machinability and performance more than any other spec decision. These are the grades a precision shop sees every week.

Metals

*Rough order of magnitude relative to 6061-T6, material and machining combined — not a quoted multiplier.

CNC machining aluminum is the highest-volume work in most shops, which is why dedicated lines exist for aluminum alloy parts, stainless steel machining and copper alloy machining. Material standards matter on the PO: 6061-T6 per ASTM B211, 304/316L per ASTM A276 and 303 per ASTM A582. Name the grade, the temper and the standard, and you remove the largest source of "wrong material" disputes. The custom aluminum milled & turned parts and precision aluminum components pages show how prototype-to-production aluminum jobs are quoted and inspected.

Engineering plastics

Plastics behave nothing like metals under the cutter: they melt instead of chip if heat builds up, absorb moisture and change size, and deflect under clamping pressure.

Choosing between grades: the engineering judgment

6061 vs 7075 — stronger does not mean stiffer. 7075-T6 carries roughly 80–90% more tensile and yield strength than 6061-T6, but their elastic moduli are nearly identical: 68.9 GPa for 6061 versus 71.7 GPa for 7075. If your part bends too much under load, switching to 7075 barely helps — stiffness comes from geometry (thicker sections, ribs), not a stronger alloy. Choose 7075 for strength- and fatigue-limited parts; choose 6061 for corrosion resistance, weldability, anodizing appearance and cost. Note 7075's trade-offs: stress-corrosion risk in T6, faster tool wear, less stable anodize color.

303 vs 304. 303 is 304 with added sulfur, which cuts 1.5–2× faster — the default for high-volume screw-machine work. The sulfur inclusions become corrosion-initiation points, so 303 belongs nowhere near a corrosive or visible environment.

304 vs 316L. If the part sees chlorides — seawater, road salt, deicing, medical fluids, chemical processing — specify 316L: its molybdenum resists chloride pitting, and the low carbon keeps welds from sensitizing. For everything else, 304 is the economical default. CNC machining stainless steel work-hardens every grade; the fix is sharp coated tooling, constant feed that never dwells on the surface, and high-pressure coolant.

Why CNC machining titanium costs what it costs. Ti-6Al-4V combines three problems: thermal conductivity of only 6.7–7.5 W/m·K (about one-sixth of steel, so heat concentrates at the cutting edge), chemical affinity that makes it gummy on tools, and a workable cutting speed of just 40–60 m/min — roughly one-tenth of aluminum. Add rapid tool wear and the result is 3–5× the machining time of a similar steel part.

Tolerances and Precision: What CNC Machining Can Achieve

Tolerance is a promise about a specific feature, not a label on the whole part. A drawing that says "±0.01 mm on this part" is asking for trouble: the same part contains easy features (a flat outer profile) and hard ones (a deep bore, a thin wall, a hole pattern across five faces). Precision CNC machining quotes are honest only when they are feature-level.

At SHENGHAO, general dimensions are held to ±0.05 mm, and ±0.02 mm is achievable on critical features with a properly designed setup — the committed tolerance is always stated in the quote before the order starts. The same feature-level approach covers our aluminum CNC machining parts for hydraulic and industrial equipment. More detail lives in our reference on tolerances on CNC machined parts.

ISO 2768: the default tolerance system

CNC machining tolerances without individual indications inherit ISO 2768-1:1989. You invoke it in the title block — "ISO 2768-mK" is the industrial default, meaning class m for linear dimensions plus class K for geometric tolerances — and every unmarked dimension inherits the table value.

Angular tolerances depend on the length of the shorter side of the angle, not the angle value:

Two housekeeping notes. Dimensions below 0.5 mm must carry an individual tolerance — the general tables do not reach them. And the system is changing: ISO 2768-2 (geometric tolerances) has been withdrawn and replaced by ISO 22081:2021, so new drawings should reference the current framework even though "mK" still appears on countless legacy drawings.

GD&T and the two dialects

Geometric dimensioning and tolerancing controls shape, orientation, location and runout with symbols. Two systems coexist, and mixing them up causes real disputes. ASME Y14.5-2018 dominates North America — note it removed concentricity and symmetry in favor of position and profile, so update drawings that still call them out. ISO 1101:2017 is the international counterpart, and the critical difference is philosophical: ISO 8015's independence principle means a dimension tolerance does not automatically control form, while ASME's Rule #1 (the envelope principle) says the size limits themselves control form. An engineer who learned ASME and reads an ISO drawing will routinely misjudge what is controlled.

A feature control frame reads left to right: geometric symbol → tolerance zone (⌀ means cylindrical) → material modifier (Ⓜ MMC, Ⓛ LMC, or nothing for RFS) → datum letters. One concept worth knowing is MMC bonus tolerance: a hole at its maximum material condition (smallest) is held to the strictest position zone, and as the hole gets bigger, extra positional tolerance is legally earned — the sanctioned way to guarantee assembly clearance, and the most misunderstood clause on a drawing. See ASME Y14.5 Dimensioning and Tolerancing for the North American standard itself.

The cost principle: tight where it matters, loose everywhere else

Tolerance bands are price steps, not a dial. Moving from ±0.05 to ±0.01 mm means slower feeds, extra finishing passes, more measurement and higher scrap risk — and ±0.005 mm often forces grinding or dedicated fixturing. The efficient drawing marks tight tolerances only on functional features (fit bores, sealing surfaces, bearing seats) and leaves everything else to ISO 2768-m. Over-tolerancing is the most common and most expensive buyer mistake, and a supplier who says so during quoting is doing you a favor. Any tight tolerance CNC machining claim should always name the feature and the inspection method behind it.

Surface Finishes for CNC Machined Parts

Finish selection is a manufacturing decision, not a cosmetic afterthought: coatings add thickness, and surface roughness affects sealing, wear and fatigue.

Anodizing and the 50/50 growth rule

Anodizing converts the aluminum surface itself into aluminum oxide — the film grows half into the metal and half out of it. That is the 50/50 rule: a Type III film of 50 µm grows about 25 µm outward on each machined surface, so a shaft plated all around gains roughly 50 µm on diameter. If your drawing calls a tight fit on an anodized feature, machine it undersize before coating or machine after coating — decide before production, not at incoming inspection.

Ra and Rz are not interchangeable

Ra is the arithmetic average of the roughness profile; Rz is the average peak-to-valley height. The same Ra can correspond to very different Rz values, and no conversion exists — if the drawing says Rz, measure Rz.

A complete spec names the parameter, the limit, the sampling length and the lay direction — "smooth" is not a spec. Most shops offer a standard menu of surface finishing options — anodizing, sandblasting, powder coating, plating, silk-screen, laser etching — with RoHS/REACH compliance confirmed on request, and machining plus finishing under one roof lets you plan coating thickness into the dimension chain instead of discovering it later. Details live in our surface finishing FAQ.

CNC Machining Cost

A CNC quote is five things added together: material, machine time, setup, post-processing and inspection, plus margin. Two quotes for the same part can differ 2–3× because they weight these differently.

Hourly rates by region and machine

Typical published ranges for 2025–2026 machine-hour rates — spindle time only, not a finished part. Rates vary with shop size, equipment age and volume; use them for planning.

The regional gap is real, and it is mostly labor, overhead and utilization — not quality. High-end aerospace and medical parts are produced in China on DMG MORI, Mazak and Haas equipment identical to what you will find in Ohio. The gap that does matter is documentation and process control, which is why the supplier checklist later in this guide spends more time on inspection than on rates.

What drives the price

How batch size amortizes setup

Setup, programming and the first article are fixed costs spread across the run: roughly 40% of the invoice on a 20-piece prototype order, below 5% by 2,000 pieces. That is the entire logic of prototype versus production pricing — and the reason merging two part versions into one release beats two small orders.

What parts actually cost

Typical ranges in 2025–2026 quotes for aluminum 6061-T6 parts, excluding special finishes unless stated:

How to reduce CNC machining cost

A DFM pass before quoting is where the money is:

• Enlarge internal radii. A 0.5 mm to 2 mm internal corner lets the shop use a larger, faster end mill — cycle time often drops 20–40%.
• Avoid deep pockets beyond a 4:1 depth-to-width ratio; they force slow step-down passes and risk tool breakage.
• Put features on fewer faces to cut setups.
• Relax non-functional tolerances to ISO 2768-m; reserve ±0.01-class bands for fits and seals.
• Keep walls above 1.5 mm where the part allows; thin walls vibrate, deflect and scrap.
• Choose stock sizes the shop already carries, and standard grades over exotic equivalents.

The pattern behind all six: cost follows cutting time and setup count, and both are set at the design stage. Every order at SHENGHAO gets a DFM review before production — where a small design change would cut cost or improve reliability, we propose it, and you decide. A quote that comes back with only a number and no manufacturability note has skipped a step. Send a drawing and request a quote: the quote comes back within 24 hours — with the manufacturability note attached.

CNC Machining vs 3D Printing and Injection Molding

The decision rule writes itself. Plastic form-and-fit models in single digits: print them. Metal functional parts, anything that must carry load, anything with a tight fit or fine surface: machine them. Identical plastic parts in five figures and up: mold them. Many programs mix all three — printed prototypes, machined first articles, molded production.

Advantages and limitations of CNC machining

The strengths: any machinable material, stock-strength parts, micron-level tolerances on favorable features, no tooling investment. The limitations are geometric — and they are the ones that surprise buyers:

• Internal corners carry the tool's radius. A sharp 90° internal corner is impossible with an end mill; every internal corner has the radius of the smallest tool that reached it.
• Deep holes get harder fast. Beyond a 3:1 depth-to-diameter ratio for blind holes (5:1 through), chips pack, drills wander and costs climb.
• Thin walls move. Below roughly 1.5 mm, cutting pressure and clamping deflect the wall, and the part springs back after release.
• Every face needs a setup unless the machine is multi-axis — setups are where cost and stack-up error live.
• Enclosed cavities cannot be machined from solid stock; that is where EDM, or a split-and-weld design, takes over.

None of these are defects. They are the boundary of the process, and designing inside it is what DFM is for. The same boundary is why shops like SHENGHAO keep adjacent processes in-house: when a part genuinely needs a molded feature or a cast body, plastic injection molding and die casting happen in one building with the machining — five processes under one roof means one supplier, one point of contact, and nobody blaming another vendor when a part is late.

Industries and Applications

Each industry's requirements show up in the quote as documentation, tolerance and finish choices.

Aerospace and defense

Structural brackets, manifolds, impeller and turbine components, landing-gear parts, fuel nozzles. Requirements: fatigue life, full material traceability, formal first-article documentation — the industry that standardized FAI reporting. See aerospace CNC machining.

Medical devices

Surgical instruments, bone screws and implants, dental components, pump and valve bodies, device housings. Requirements: biocompatibility, cleanliness, lot-level traceability. See CNC machining for medical devices.

Automotive and EV

Sensor housings, valve bodies, transmission components, turbo parts, EV battery structural components. Requirements: consistency at volume — thousands of identical parts, tight cost control, quality systems built around PPAP and SPC. See CNC parts for automotive suppliers.

Robotics and industrial automation

Robot joint housings, harmonic drive components, lead screws, linear guide rails, servo end covers, fixtures and jigs. Requirements: position accuracy and wear resistance — a robot that holds calibration after a million cycles. See CNC machining for industrial automation.

Electrical and electronics

Heat sinks, enclosures, connector bodies, RF housings, shielding components. Requirements: thermal performance, RoHS/REACH compliance, surface appearance. See CNC machining for electrical and electronics.

Consumer products and sports

Bicycle frames and components, golf club heads, hiking hardware, fitness equipment, custom housings and prototype enclosures for product launches. Requirements: lightweight alloys, fatigue strength, surface finish. See CNC parts for sports & fitness equipment.

How to Choose a CNC Machining Supplier

Most buyers evaluate quotes; the better move is to evaluate the shop behind the quote. This checklist separates a capable contract manufacturer from a broker.

1. Equipment list. Axis count, brands, quantity, maximum work envelope. A shop that runs 3/4/5-axis, EDM and grinding in-house quotes one setup where another quotes a relay between subcontractors.
2. Inspection capability. Is there a CMM, a roughness tester, hardness testers? Can they balloon your drawing and issue a full dimensional report? Inspection capability is the hardest thing to fake.
3. Material control. Do mill test reports (EN 10204 3.1 or equivalent) ship with the parts, traceable by heat number? Is there incoming inspection and retained samples from every batch?
4. DFM quality. Does the quote return with manufacturability notes, or just a number? A shop that flags an expensive, fragile or impossible-as-drawn feature before the order is protecting your budget.
5. Communication. How fast do technical answers come back, and who writes them? The strongest signal is whether the person reviewing your drawing is the person who will plan the work.
6. Sample validation. Pay for a first article before committing volume — one paid sample tests quality, documentation and delivery simultaneously.
7. IP protection. Will they sign a mutual NDA, and is your CAD access-controlled? Drawings leaking to a competitor's quote is a real failure mode.
8. Certificate honesty. Verify any claimed certification against the issuing body, with scope and expiry checked. A shop that overstates documents will overstate delivery dates.
9. Lead-time commitment. Written dates and a defined escalation path when something slips. Silence during quoting predicts silence during production.
10. Quote transparency. The breakdown should itemize programming, fixtures, first article, deburring, inspection, finishing, packaging and freight. A low headline price with costs "to follow" is the classic red flag — along with vagueness about material certs, sluggish quote-phase responses, and pressure to accept an uncommitted lead time.

Notice what this checklist rewards: process evidence, not adjectives. SHENGHAO's approach maps onto it — committed tolerances stated in the quote, FAI before production with in-process and final inspection plus a dimensional report with the parts, retained samples for traceability, material certification with every aluminum component, DFM on every order, and quotes back within 24 hours because the engineer who reviews your drawing plans your job. That last point matters more than it sounds: technical questions get answered once, correctly, by the person accountable for the outcome.

For a deeper look at working with a CNC machining manufacturer in China — including how to verify a factory's claims and structure an RFQ — see our companion guide on how to choose a CNC machining supplier in China.

MOQ, Lead Time and Getting a Quote

Minimum order quantity

Most CNC shops have no hard MOQ — they will machine a single piece — but every job carries a minimum charge covering setup, programming and the first article. The honest question is not "do you have a MOQ" but "what is the minimum charge, and at what quantity does the piece price drop?"

Small orders reveal a shop's real priorities. At SHENGHAO the minimum order is 20 pieces, treated as a real order rather than a sample — small batches are scheduled like any other job, and nobody cares less about your work because a bigger order called. The mechanics behind that commitment, and how setup costs are itemized, are covered in our reference on the 20-piece MOQ for CNC machining. Whatever the shop, two habits pay for low-volume CNC machining: order one merged batch rather than several small releases, and keep prototype and production quotes separate so you can see exactly what setup amortization buys you.

Lead time

Always ask when the clock starts — purchase order, drawing approval or material arrival — and whether outside processing and shipping sit inside the quoted window.

File formats

STEP (AP203/AP214) is the preferred 3D format; IGES, Parasolid (X_T), DWG and PDF drawings all work. The ideal package is a 3D file plus a 2D PDF drawing with critical dimensions and tolerances called out — the model carries geometry, the drawing carries intent. An STL file alone cannot define a tolerance, so if that is all you have, expect a round of questions. Format-by-format detail is in our notes on file formats for a CNC machining quote.

CNC Machining FAQ

What is CNC machining?

CNC machining is a subtractive manufacturing process in which a computer program controls machine tools that remove material from a solid workpiece until the part matches a CAD model. It covers milling, turning, grinding, EDM and more, across metals and plastics.

How does CNC machining work?

The process runs five steps: a CAD model is created, CAM software generates a toolpath and post-processes it into G-code, the blank is clamped and datum-ed in a setup, the machine cuts the part, and the result is inspected — typically first-article inspection on critical parts, then in-process and final checks. G-code drives axis motion while M-code controls auxiliary functions like spindle start and coolant.

What are the different types of CNC machines?

The main families are milling machines (3-, 4- and 5-axis), CNC lathes and turning centers, mill-turn centers, Swiss-type lathes, wire EDM and sinker EDM, grinders, and cutting platforms like waterjet, plasma and laser. Milling handles prismatic parts, turning handles rotational parts, and EDM cuts hardened conductive materials without cutting force.

What materials can be CNC machined?

Almost any metal and most engineering plastics: aluminum 6061 and 7075, stainless 303/304/316L and 17-4 PH, brass C36000, copper C11000, titanium Ti-6Al-4V, carbon and alloy steels like 1018, 1045 and 4140, plus plastics such as POM, PEEK, PA66, PC, ABS, PMMA, PTFE, PBT and PPS. The practical limit is machinability.

What tolerance can CNC machining achieve?

Standard machining holds ±0.05–0.1 mm, precision work reaches ±0.01–0.02 mm, high-precision setups achieve ±0.005–0.01 mm, and ultra-precision grinding reaches ±0.001–0.002 mm. Tolerance is a feature-level promise, not a part-level label — deep holes, thin walls and multi-face hole patterns are the hard cases.

How much does CNC machining cost?

Machine-hour rates run roughly $20–40/hr for 3-axis work in China versus $60–120/hr in the US, with 5-axis at $45–90/hr in China and $120–250/hr in the US. In piece-price terms, a simple aluminum bracket lands around $60–130 for one piece and $6–12/pc at 100 pieces.

What is the difference between 3-axis and 5-axis CNC machining?

A 3-axis mill moves the tool in X, Y and Z and machines everything reachable from one direction; extra faces require re-clamping, which adds cost and stacks positioning error. A 5-axis mill adds two rotary axes so the tool approaches from any angle, completing five faces in a single setup with no re-registration error.

What is the difference between CNC milling and CNC turning?

Milling holds the workpiece fixed and spins the cutting tool — it makes flats, pockets, profiles and complex non-rotational shapes. Turning spins the workpiece against a fixed tool — it makes shafts, bushings, nuts and other rotational parts. Mill-turn centers do both in one setup for parts that need a turned body with off-center milled features.

CNC machining vs 3D printing: which should you choose?

Choose 3D printing for plastic prototypes and form-and-fit models in quantities of one to twenty, where speed matters more than strength or tolerance. Choose CNC machining for metal parts, load-bearing components, tight fits and anything above twenty pieces — machined parts keep stock-material strength and hit tolerances printing cannot.

What surface finishes are available for CNC machined parts?

Aluminum parts typically get Type II anodizing for color and corrosion protection or Type III hard coat for wear; steel gets zinc, nickel or chrome plating or powder coating; stainless gets passivation; medical and food parts get electropolishing. Coatings add thickness — a 50 µm anodize film grows about 25 µm per surface — so tight fits must be planned before coating, not after.

What is the minimum order quantity (MOQ) for CNC machining?

Most CNC shops have no hard MOQ and will machine a single piece, but every job carries a minimum charge covering setup, programming and first-article inspection. Many manufacturers set a practical floor around 20 pieces, treating small batches as scheduled orders rather than favors.

How long does CNC machining take?

Simple prototypes take 3–7 working days, moderate-complexity batches 7–14 days, multi-process or 5-axis work 14–30 days, and small-batch production runs of 25–500 pieces typically 3–6 weeks. The critical detail is when the clock starts — purchase order, drawing approval or material arrival — and whether outside processing and shipping are included.

Conclusion

CNC machining remains the default process for precision parts because it combines stock-material strength, tight tolerances, any machinable material and no tooling investment. The buyer's edge is not finding the cheapest hourly rate — it is specifying the part so the rate applies to the right machine, with tolerances only where function demands them, and a supplier whose process evidence stands behind the quote.

If you have a part or a custom CNC machining project to quote, send a drawing (STEP, IGES, X_T, PDF or DWG) with quantities and material to info@shenghaotech.com. You will have a quote within 24 hours, with a manufacturability note on anything worth changing. If you are not ready to share drawings, describe the problem you are solving and we will tell you honestly whether we are the right shop for it. And if you would rather see before you buy, you are welcome to visit our factory in Zhuhai or request a live video tour — the floor, the inspection room and a job in progress. Start anytime via request a quote.