The Devil in the Decimal: Auditing a Chinese CNC Quotation Before Your Purchase Order Goes Out

A Chinese CNC quotation usually arrives as a two-page PDF: a logo, a unit price, a lead time, a validity date, and one line confirming that tolerances are "as per drawing". It reads like a price list. In practice it is the opening draft of a contract, and the clauses that will decide whether the job goes well are the ones that were never written at all.

What follows is a forensic reading of that document, written for UK engineers and buyers who are close to raising a purchase order. The objective is not to distrust every supplier. It is to convert a sales document into a risk map you can act on before the money moves.

The Silences Matter More Than the Numbers

The unit price is the least informative figure on the page. What determines your true landed cost — material specification, inspection evidence, freight terms, tooling ownership, remedies for non-conforming parts — sits in the gaps. A useful discipline is to read the quote twice: once for what it says, and once for what a competent European supplier would have specified and this one has not.

Clauses 1 and 2: Scope, Quantity Breaks and the Definition of a Part

Establish precisely what is being priced. Does the unit rate include deburring, chamfering, cleaning and protective packaging, or are those extras? Are secondary processes — anodising, passivation, zinc plating, heat treatment — subcontracted, and is the subcontractor named? Ask for a price at one, ten, one hundred and one thousand pieces. A flat rate across all four bands is a strong hint that you are talking to a trading house rather than a machine shop with its own spindles.

Clause 3: Tolerance Callouts and Drawing Precedence

Most quotes defer to the drawing, which is fine in principle and dangerous in practice. Insist that the drawing explicitly invokes ISO 2768-m for general tolerances; the Chinese GB/T 1804-m grade is broadly aligned, but the reference should be stated, not assumed. Decide and record which document governs in a conflict: the 3D model or the 2D drawing. Critical features — bores with fits, datum-referenced faces, anything feeding a bearing or a seal — should be listed separately and priced as CMM-verified characteristics. A blanket claim of "all dimensions to plus or minus 0.05 mm" across a large part is a warning sign, not a comfort.

Clause 4: Material Equivalents Between BS/EN and GB Standards

This is where UK buyers most often get caught. Chinese stock is specified to GB/T designations, and substitution is routine. Some pairings are sound: 1.4301 (304) maps to 06Cr19Ni10, 1.4404 (316L) to 022Cr17Ni12Mo2, and S355 to Q355 under GB/T 1591. Others are looser. Q235B is frequently offered as a substitute for S275 and is not equivalent in yield. The EN AW-6082 grade familiar from BS EN 755-2 has no direct GB/T counterpart and is commonly replaced with 6061-T6, which is a close cousin rather than an interchangeable material for fatigue or structural duty.

Ask for EN 10204 type 3.1 mill certificates for every heat, and check the issuer: a certificate from the stockholder is not the same as one from the steel mill. Where a substitution is proposed, require it in writing with the mechanical properties stated, and have your own engineer sign it off.

Clause 5: Incoterms — Where Risk Actually Changes Hands

The quote should name an Incoterms 2020 rule and a precise place. FOB Shenzhen or FOB Ningbo is conventional and gives you control of freight. CIF is convenient but check the insurance level; the minimum cover is thin. DDP looks tidy and often is not: if the seller acts as importer of record, you may find yourself unable to recover import VAT through postponed VAT accounting. EXW is awkward in China because export clearance sits with the buyer under the rule. For most UK buyers, FOB origin or DAP your premises, with your own EORI number as importer, is the cleanest structure.

Clause 6: Payment Milestones

Thirty per cent deposit and seventy per cent before shipment is normal, and acceptable where the balance is released against a pre-shipment inspection report rather than a photograph of a pallet. Be cautious with 100 per cent upfront on a first order. For smaller values, an escrow-style platform arrangement gives you a dispute route. Above roughly twenty thousand pounds, a letter of credit or documentary collection is worth the bank charge.

Clause 7: Tooling, Fixtures and Programme Ownership

If you are paying a tooling charge, you are buying an asset. Say so. The quote should list dedicated fixtures, moulds, gauges, CAM programmes and CMM programmes, state whether the charge is one-off or amortised into the piece price, and confirm that ownership transfers to you. If amortised, agree the point at which it transfers and a replacement value. Add a right to collect the tooling at your cost if the relationship ends.

Clause 8: Inspection Reports and What 'Passed' Actually Means

A tick sheet proves nothing. Require a first article inspection report for a new part, with actual measured values, the datum alignment stated, and the gauge or machine identified. Ask for CMM reports in a named format, material certificates, and surface treatment evidence — anodising thickness to BS EN ISO 7599, RoHS and REACH declarations for plated parts. Agree a sampling plan to ISO 2859-1, which is harmonised with GB/T 2828.1, including the AQL level. Confirm that the measuring equipment is calibrated to a traceable standard, ideally through a CNAS-accredited laboratory.

Clause 9: Lead Time and Its Start Date

Is the quoted lead time in working days or calendar days, and does it run from the purchase order, from drawing approval, or from material arriving on site? A twenty-day lead time that starts when the aluminium lands can be fifty days in reality. Ask for a milestone schedule: material received, first article complete, production complete, shipped.

Clause 10: Duty, VAT and the Import File

The quote cannot answer this, but the purchase order must. Confirm the commodity code before shipping — classification of machined components depends on the process and material, and an error at origin becomes your liability at the border. You will need an EORI number and a customs declaration through CDS. Import VAT at 20 per cent on the customs value plus duty is recoverable if you are VAT-registered and use postponed VAT accounting; duty is not. Check the UK Trade Remedies Authority register, because certain product categories — aluminium extrusions among them — carry anti-dumping duties that can dwarf the unit price saving.

Clause 11: The Boilerplate Deserves a Second Read

Look at the currency clause and who absorbs sterling movements against the renminbi or dollar. Look at validity: thirty days is standard and puts all FX risk on you after that. Look at the remedy for non-conforming parts — rework, replacement or credit, and crucially who pays the return freight. Look at the liability cap and the dispute route; CIETAC arbitration in Beijing is common, and a neutral seat such as Hong Kong is often a reasonable compromise to propose.

Turning the PDF into a Risk Map

Score each of the eleven areas red, amber or green, and treat any silent clause as amber by default. Most quotes that fail do so on four or five amber items rather than one red one, and the amber items are the ones a short, specific email can fix before the PO is issued.

Before you commit, send eleven questions: which standard governs general tolerances; which document takes precedence; who issues the mill certificates; is any substitution proposed and on what basis; which Incoterm and named place; what the balance payment is released against; who owns the fixtures; can we see a sample CMM report; when exactly the lead time clock starts; what commodity code will appear on the export documents; and which dispute forum applies. A supplier who answers all eleven clearly within two working days has told you something genuinely useful about how they will behave when a batch goes wrong.