How to Get Accurate CNC Machining Quotes From China (RFQ Guide)

The same CNC part drawing sent to multiple Chinese CNC factories can return quotes that vary by 3x or more for identical parts. That variance is rarely about which factory is more expensive. It's about which factory made which assumptions when the RFQ left out information they needed to price the job accurately.

The scale of the problem is consistent across procurement teams. We've seen in the majority of Haizol's calls that quote fragmentation comes up as the the primary pain point. Not cost, and not lead time. Incomplete specifications are the most common root cause, when factories can't calculate scope, they price for uncertainty, which inflates quotes by 15-25% above what a complete RFQ would return.

This guide covers exactly what to include in a CNC machining RFQ for China-sourced parts, why each element closes an interpretation gap that otherwise costs money, and how to structure your request to get comparable quotes from multiple verified CNC factories.

TL;DR / Key Takeaways

• The minimum correct file package is STEP + 2D PDF. Sending either one alone produces incomplete quotes.
• Incomplete RFQs trigger a 15-25% risk premium - factories price for uncertainty when they can't calculate scope.
• Specify material to grade and temper (e.g., aluminum 6061-T6, not just “aluminum”). Missing the temper has scrapped entire production runs.
• Default to Ra 3.2 µm surface finish. Going to Ra 0.8 µm doubles machining time relative to Ra 1.6 µm. Only tighten where function requires it.
• Submit your RFQ to verified factories only. A verified profile tells you whether the factory's equipment can actually support the tolerance you're quoting.

Why Do CNC Machining Quotes from China Vary So Much?

Quote variance from Chinese factories is not a China problem. It's a specification problem. Factories don't quote your drawing. They quote their interpretation of it. And when information is missing, every factory interprets the gaps differently.

Why Incomplete Specifications Add Cost

Factories face two choices when an RFQ is missing critical information: stop and ask questions, or make assumptions and quote what they think you mean. Both paths cost you.

Back-and-forth emails add days to a quotation cycle. Factories protect themselves by adding a risk premium of 15-25% to the price when they can't calculate scope. Industry data shows engineers can spend up to 30% of their time resolving clarifications that a complete RFQ would have prevented.

What is a risk premium? A risk premium is the buffer a factory adds when it can't fully calculate machining scope. Missing tolerances, vague surface finish requirements, or an unspecified material grade all force the factory to price for the worst-case interpretation. That buffer is not a negotiating tactic. It's the factory protecting its margins against uncertainty you introduced. Remove the uncertainty and the premium disappears.

Drawing Standard Differences

Chinese factories often default to GB/T 1804, which is China's national standard - and an equivalent of ISO 2768. The tolerance values are identical. But ASME Y14.5 drawings, which are common among US and some European engineering teams, carry different conventions, particularly for form tolerances and datum structure.

A Chinese factory receiving an ASME drawing can interpret geometric tolerance zones through ISO conventions. The result is parts that pass the factory's internal inspection and fail your incoming inspection, not because anyone made a manufacturing error, but because the tolerance zone was read differently.

Surface finish adds another layer. For example, ISO 4287 and ASME B46.1 specify different default cut-off lengths for Ra measurement. The same Ra number on a drawing means a different surface texture depending on which standard the factory's roughness tester is calibrated to. Specifying the cut-off length explicitly eliminates this gap.

What Files Do You Need to Send for a CNC Machining Quote?

The correct file package for a CNC machining quote is a STEP file (3D geometry) and a 2D PDF drawing (tolerances, notes, and intent). Sending either one without the other forces the factory to fill in the gaps causing them to fill it differently.

STEP File (.STP) Format

STEP (ISO 10303) stores part geometry as solid B-rep data: mathematically defined surfaces connected into a closed 3D model. When a factory's CAM software imports a STEP file, it reads true curves and feature relationships. That's what toolpath planning and cycle-time estimation require.

STEP is the universal standard. It's compatible with every major CAD and CAM platform and imports as a watertight solid without surface gaps. When you export from SolidWorks, Fusion 360, CATIA, or any mainstream CAD tool, STEP is the format that transfers without information loss.

Before sending a STEP file to a CNC factory, verify these 3 things:

• Confirm the STEP file is a watertight solid: The export produces a watertight solid, not a surface model or mesh. Open it in a free viewer (eDrawings or Autodesk Viewer) and confirm it renders as a closed solid body with no open surfaces.
• Make sure the STEP file matches the correct revision: The file references the correct revision. Export from the same revision your 2D drawing specifies, a mismatch between 3D geometry and 2D intent is one of the most common quoting errors.
• Use a clear filename with the part number and revision: The filename reflects the part number and revision (e.g., BRACKET_PIVOT_REV_C.stp). Factories handle files from multiple buyers simultaneously and need unambiguous filenames.

If STEP export is unavailable, IGES (.igs) is an acceptable fallback. It carries NURBS surface data rather than solid geometry, which can produce minor surface gaps on import. If you send IGES, note it in your RFQ and ask the factory to confirm the import is clean before quoting.

2D PDF Drawing Format

The 2D drawing communicates everything the 3D model cannot: tolerance callouts, GD&T symbols, surface finish requirements, thread specifications, material callout with grade and temper, and technical notes. It also carries the part number, revision level, and date - which establish which version of the design is being quoted.

Without the 2D drawing, a factory can see the shape but cannot know how tightly it must be controlled, what the surface needs to be, or what the material must achieve. The STEP file is the geometry. The PDF is the intent.

What should a 2D PDF drawing include for an RFQ?

• Title block: Part number, revision letter, material callout (to grade and temper), drawing date, and scale
• General tolerance standard: "ISO 2768-m" or "ASME Y14.5" stated in the title block - this applies to every unspecified dimension automatically
• Critical feature callouts: GD&T symbols and explicit tolerances on the 3-5 features where function demands it - bearing bores, sealing surfaces, locating datums
• Surface finish: A default Ra value in the notes block (Ra 3.2 µm for standard finish), plus tighter values called out on individual surfaces where required
• Thread specifications: Thread form, class, and pitch for every threaded feature (e.g., M6×1.0-6H)
• Notes block: Material certification requirements, special handling instructions, or any process restrictions relevant to machining

What to leave out at the RFQ stage: assembly context drawings, cost-sensitive notes, and downstream application details not needed for machining the part itself.

Other Formats and Their Limitations

DXF is a 2D format used for laser cutting, waterjet cutting, and CNC routing of flat profiles. It carries no depth data and cannot represent 3D geometry. Sending a DXF for a machined part forces the factory to reconstruct 3D geometry from a 2D profile - an interpretation exercise that introduces error before a single chip is cut. Use DXF only for genuinely flat parts being cut from sheet material.

STL files are triangle mesh approximations designed for 3D printing. The mesh facets are not true geometry and cannot represent curved surfaces accurately enough for tight machined tolerances. Never use STL for a CNC machining quote.

File Format	Data Type	For CNC Machining	Notes
STEP (.stp)	Solid B-rep	Yes - preferred	Universal, watertight, true geometry
IGES (.igs)	Surface NURBS	Acceptable (caution)	Legacy format; may have surface gaps
DXF (.dxf)	2D vector	No (3D parts)	Correct for laser/waterjet flat profiles only
STL (.stl)	Triangle mesh	No	For 3D printing only; mesh approximation is not suitable for machined tolerances
PDF (2D drawing)	Technical drawing	Yes - required	Carries tolerances, GD&T, finish, material callout

How Do You Specify Material, Tolerances, and Surface Finish in a CNC RFQ?

To specify material, tolerances, and surface finish in a CNC RFQ, use measurable manufacturing requirements: exact material grade and temper, a general tolerance standard, critical feature tolerances, and Ra surface finish values. These fields should not be left open to supplier interpretation.

Material Grade and Temper

Specify material to grade and temper, not just the material family. “Aluminum” is not a specification. It leaves the factory choosing an alloy - and they will choose based on availability or cost, not your application.

Write “aluminum 6061-T6” (general precision machining), “aluminum 7075-T651” (high-strength aerospace applications), or “stainless steel 316L per ASTM A276” (corrosion-resistant medical or marine parts). A documented failure case: an engineer specified “aluminum 7075” without the “-T6” temper designation. The factory used available untreated material. Parts were dimensionally correct and failed strength testing - entire run scrapped. The fix was one word on the drawing.

Tolerance Callouts

General tolerances cover every dimension that doesn't carry its own explicit callout. “ISO 2768-m” in the drawing title block applies a medium-class tolerance to all unspecified linear and angular dimensions - it's the correct baseline for most commercial precision parts. You don't need to annotate every feature.

What you do need to annotate: the 3-5 features that are critical to function - sealing surfaces, bearing fits, mating bores, and locating datums. The cost of tighter tolerances is exponential, not linear:

Tolerance	Cost Multiplier	Typical Use
±0.1 mm	1x (baseline)	General dimensions, non-critical features
±0.05 mm	1.3-1.5x more	Mating bores, locating datums
±0.01 mm	3-5x more	Bearing journals, sealing surfaces

Tight tolerances on non-critical features inflate cost without improving the part. Reserve tight callouts for dimensions where failure to hold them causes a functional problem.

Surface Finish Ra Values

Ra 3.2 µm is the standard as-machined finish. It's what comes off the CNC machine with normal cutting parameters - visible tool marks, functional for most industrial applications. It adds zero cost beyond machining time.

Ra 1.6 µm requires a dedicated finishing pass and adds 15-25% to cycle time. Ra 0.8 µm - required for bearing journals and sealing surfaces - doubles machining time relative to Ra 1.6 µm and often requires grinding as a secondary operation. Going from Ra 3.2 µm to Ra 0.8 µm can increase machining time by 200-400%. Default to Ra 3.2 µm for all surfaces that don't have a specific functional requirement. Specify tighter only where you can explain why that surface needs it.

How Does Quantity Affect CNC Machining Quotes from China?

Quantity is not just a commercial variable - it changes how a Chinese factory structures its entire machining approach. Sending a single-quantity RFQ for a part you intend to order at scale produces a quote that won't reflect production economics.

Quantity Tier Pricing

Request pricing at 3 quantity points: your immediate prototype quantity, a mid-range test run, and your anticipated production lot. This reveals where setup cost gets amortized across volume - the clearest signal of whether a factory is economically suited to your actual demand.

Setup cost is fixed regardless of quantity. A factory that quotes 1 part and 50 parts at the same unit price hasn't separated setup from material. A factory that shows meaningful unit cost reduction at volume has done the calculation correctly and is quoting production economics, not prototype pricing.

Production Intent and Annual Volume

Annual volume changes the factory's tooling and scheduling assumptions. A factory that knows you'll order 2,000 parts per year will invest in dedicated fixtures and optimized tooling. A factory quoting a one-time order of 20 parts will not.

State prototype or production intent explicitly in your RFQ. If you're requesting prototype pricing, say so - and if you expect to move to production, give the expected annual volume. Factories that understand your total demand quote strategically; those that don't, quote conservatively.

How Do You Compare CNC Machining Quotes from Multiple Chinese Factories?

To compare CNC machining quotes from multiple Chinese factories, first make sure every factory is quoting the same technical requirement. Use the same STEP file, 2D drawing, material grade, tolerance standard, surface finish requirement, and revision level for every supplier. Then compare price, lead time, inspection capability, machine fit, certifications, and available capacity.

A low quote is only useful if it reflects the same part, same quality requirement, and same delivery expectation.

For example:

What to compare	Why it matters	Where to check
Price	Shows the commercial offer	Quote details
Lead time	Shows delivery feasibility	Quote details
Machine capability	Confirms whether the factory can make the part	Verified factory profile
QC equipment	Confirms whether tolerances can be inspected	Verified factory profile
Certifications	Confirms quality or industry requirements	Verified factory profile
Capacity	Shows whether the quoted lead time is realistic	Verified factory profile

Why CNC Machining Quotes Vary Between Factories

CNC machining quotes vary because factories apply different assumptions when an RFQ is incomplete.

One factory may interpret an unspecified surface finish as Ra 3.2 µm. Another may assume Ra 1.6 µm. One factory may quote local aluminum billet. Another may quote imported certified billet. One may include CMM inspection. Another may include only basic dimensional checks.

These factories are not necessarily quoting incorrectly. They are quoting based on their own defaults. The buyer’s job is to remove those defaults before comparison.

To reduce quote variance, specify:

• Material grade and temper
• General tolerance standard
• Critical feature tolerances
• Surface finish requirements
• Inspection requirements
• Quantity
• Delivery location
• Drawing revision level

When those requirements are fixed, quote differences are easier to interpret. Price differences are more likely to reflect factory capability, available capacity, and CNC machining cost structure, not different assumptions about the part.

How to Compare CNC Quotes Against Factory Capability

A CNC quote should be evaluated against the factory’s ability to make and inspect the part.

A verified factory profile gives you the data to evaluate whether a quote is credible, not just competitive. Look at the machine list: does the equipment support the tolerance claim? A factory quoting ±0.025 mm with no CMM (coordinate measuring machine) listed under QC equipment cannot verify that tolerance. The claim is not auditable.

Check remaining capacity against the quoted lead time. A factory at 92% utilization quoting 15-day delivery is not being realistic. On Haizol's verified factory profiles, machine lists, certifications, and capacity data are each independently confirmed before the factory can receive any RFQ. 90% of RFQs submitted through Haizol receive quotes from 8 or more verified factories within approximately 24 hours.

Once your RFQ is submitted, all factory quotes are waiting in your account. Here is how to get to them:

Step 1: Open Your RFQ dashboard

After logging in, click the profile icon in the top-right corner of the Haizol platform. A dropdown menu will appear. Select RFQs from the options to go to your RFQ dashboard.

Step 2: Select the Part You Want to Review

Your RFQ dashboard lists all the parts you have submitted for quoting. Click on the specific part or product you want to check. This opens the RFQ detail page for that item.

Step 3: Open the Quotes Tab

Click the Quotes tab to see all factory responses. Inside the RFQ detail page, click the Quotes tab. This shows every quote submitted by verified factories for that part - including price, lead time, and a link to the factory's verified profile. Price differences between factories are visible here, so you can compare what each factory is actually offering before making a decision.

Frequently Asked Questions

What Is the Minimum RFQ Package for a CNC Machining Quote From China?

The minimum correct package is a STEP file, a 2D PDF drawing with tolerances and material callout, quantity (or quantity tiers), and your target lead time. Missing any one of these forces the factory to make assumptions - which shows up as a higher price, a longer response time, or both.

What Happens if I Only Send a 2D Drawing Without a 3D File?

The factory can read tolerances and material from the drawing, but cycle-time estimation and toolpath planning require solid geometry. For simple prismatic parts, a 2D drawing may be enough for a rough budget quote. For any part with curved surfaces, complex pockets, or multi-axis features, the 3D STEP file is required for a reliable quote.

How Do I Know if a Chinese Factory Can Hold My Tolerance?

Look at the equipment list on their factory profile. A CMM in the QC section is the minimum instrument required to verify tolerances of ±0.025 mm or tighter. A factory without a CMM cannot perform first-article inspection to tight-tolerance drawings - whatever the quote says.

How Many Quotes Should I Request for a CNC Machining Job?

8 or more verified factory quotes give you enough spread to identify the real market price for your part, not just the loudest quoting behavior. Getting fewer than 5 quotes leaves you vulnerable to pricing outliers in either direction - one unusually cheap quote from a factory that hasn't costed the job correctly, or one unusually expensive quote inflating your budget.

Should I Share My Full Assembly Files With Chinese Factories at the Quote Stage?

No. Share manufacturing drawings at the RFQ stage - the 2D drawing and 3D STEP model for the specific part being quoted. Reserve assembly files, source models, and proprietary process data for the awarded supplier after an NDA is in place.

What Is the Difference Between Prototype and Production Pricing for CNC Machining in China?

Prototype pricing absorbs setup cost across a small quantity. Production pricing amortizes that same setup cost over a larger run - the fixed cost gets spread, and unit price falls. A prototype price of $85 per part for 5 units can drop to $22 per part at 500 units once setup, tooling, and fixture cost are spread across volume. If you're requesting prototype pricing, state that clearly - and request production pricing at your expected volume so you can plan the economics accurately.

Compare Your Next CNC RFQ with Confidence

Good quote comparison starts with a complete RFQ package. When every factory receives the same STEP file, 2D drawing, material grade, tolerances, finish requirements, quantity, and revision level, price differences become easier to understand.

The lowest quote is not always the best quote. The right supplier is the one with the machine capability, inspection equipment, capacity, and quality systems to make the part correctly.

With Haizol, you can submit one RFQ and compare quotes from 8+ verified CNC factories within approximately 24 hours. Each quote links to a verified factory profile, so you can check capability before awarding the job. Ready to compare your next CNC RFQ?