How to Write an RFQ That Gets an Accurate Machining Quote

You send an RFQ to three suppliers. One quotes in a day, one takes a week and comes back with four questions, and the third quotes fast but 40% higher. You can't tell which is the real price because you gave each of them something slightly different. That is not a supplier problem. That is an RFQ problem.

A request for quotation is a procurement document, not a file attachment. Its job is to make a supplier's estimator confident enough to commit a number without guessing. Every gap in the RFQ becomes either a guess priced high for safety, or a question that adds days. This guide covers exactly what belongs in a machining RFQ package, why each item is there, and what a missing item does to the quote you get back.

Two adjacent topics are covered elsewhere and are not repeated here: the mechanics of submitting a request and what moves the price live in how to get an instant CNC machining quote, and the CAD file specifics — formats, exporting, watertight geometry — live in how to prepare CAD files for a CNC quote. This article is about the package as a whole: completeness and comparability.

The quick answer: what a complete RFQ contains

A machining RFQ that gets an accurate, first-pass quote contains nine things. Miss any one and the estimator either pads the price or asks you a question.

1. 3D model (STEP preferred) — the geometry that gets machined.
2. 2D drawing (PDF) — tolerances, datums, critical features and intent the model cannot carry.
3. Material grade and acceptable substitutes — the exact alloy, plus what you will and won't accept instead.
4. Critical vs general tolerances — which few features are tight, and a general tolerance for everything else.
5. Surface finish and treatment — machined finish (e.g. Ra 0.2 µm), plus anodising, plating or painting.
6. Quantity and likely repeat volume — this order, and whether it repeats.
7. Inspection and documentation — FAI, CMM report, material certificates.
8. Target date — when you need parts in hand.
9. Compliance and packaging — RoHS/REACH, marking, export packaging, Incoterms.

The rest of this guide takes each of these and explains what it costs you when it's absent.

Why the model alone is not enough

The most common RFQ mistake is sending only a STEP file. A 3D model is a perfect description of nominal geometry and nothing else. It carries no tolerances, no datum references, no surface-finish callouts, no thread specifications you can rely on, and no indication of which faces are functional and which are cosmetic. The model says "this is the shape." It does not say "this bore has to be H7 and everything hangs off it."

When a supplier receives a model with no drawing, one of two things happens. A careful supplier emails you back asking for tolerances, material and finish — a clarification round that typically costs two to four days before you even have a number. A careless supplier assumes standard tolerances everywhere, quotes low, and then the parts come back out of spec on the one feature you cared about, because you never told them it was critical. Both outcomes are worse than spending twenty minutes on a drawing.

Model-based definition (a fully annotated 3D model with PMI) does exist and can replace a 2D drawing, but only if your PMI is complete and the supplier's CAM chain reads it. For most cross-border RFQs, a plain PDF drawing on top of the STEP file is faster, unambiguous and universally readable. Send both. The ISO 128 drawing conventions and ASME Y14.5 GD&T standards exist precisely so a drawing means the same thing in Guangzhou as it does in Stuttgart.

What each item does to your quote

Here is the core of it: the RFQ checklist as a working table. Read the third column — that is what an omission actually costs.

Material grade and substitutes

"Aluminium" is not a material. 6061-T6 and 7075-T6 differ in price, machinability and strength; a supplier quoting on the wrong assumption gives you a number you can't use. Name the grade. Then, separately, tell the supplier what substitutes you accept. If 6061-T6 and 6082-T6 are functionally interchangeable for your part, saying so lets the supplier quote whichever is in stock — often faster and cheaper. If nothing but the exact grade will do, say that too, so no one assumes flexibility you don't have. Sendot machines 30+ materials; the more precisely you name the grade, the tighter the quote.

Critical vs general tolerances — the top avoidable cost

This is where most money is wasted before a single chip is cut. Applying a tight tolerance to every dimension — "±0.01 mm all over" because it feels safe — is the single biggest avoidable cost driver on a machining quote. Tight tolerances mean slower feeds, more passes, more in-process inspection, higher scrap and sometimes a grinding operation instead of a milling one. Most of a typical part does not need it.

Do the opposite. Identify the handful of features that are actually functional — the bearing bore, the mating face, the dowel-pin holes — and tolerance those tightly. Sendot holds ±0.05 mm on critical features and Ra 0.2 µm where required. Then put a sensible general tolerance in the title block (an ISO 2768-m or -f class, for instance) so every unmarked dimension is covered by one rule. A drawing that marks three critical dimensions and defers the rest to a general class quotes far lower than one that is silently tight everywhere — and it inspects faster too.

Quantity and, crucially, repeat volume

Quantity sets the per-part price, so an RFQ without it can't be priced at all. But repeat volume changes the process. A one-off prototype is best machined; a part you'll order 2,000 of every quarter may be cheaper cast or moulded with tooling. Die casting at Sendot carries a tooling-based MOQ of 1,000–3,000 pcs, while CNC and sheet metal have no MOQ. If you tell the supplier "50 now, likely 3,000/year if it works," a good estimator can quote the prototype on CNC and flag the tooling path for volume — so you don't machine 3,000 parts one at a time next year at ten times the unit cost.

Surface finish, inspection and documentation

State the machined finish and any treatment — anodising, plating, powder coat, bead blast — because treatments are outside operations with their own cost and lead time. Then state inspection needs explicitly. A first-article inspection (FAI) report, full-dimensional CMM data, or material certificates each add real hours and belong in the price up front. Sendot provides CMM inspection, FAI reports and material certificates under its ISO 9001 system — but only what you ask for gets quoted. If your part feeds a medical or automotive program with its own quality-system requirement (ISO 13485, IATF 16949), name that requirement in the RFQ so the supplier can confirm which documents it can supply for your supply chain, rather than discovering the gap at PPAP.

A worked RFQ: the step-by-step

Here is a repeatable way to assemble the package so nothing slips.

1. Export the model. STEP (AP214) is the safe default; Sendot also reads IGES, X_T, DWG, PDF, STL, and DXF for 2D laser parts. Details in the CAD-prep guide.
2. Make the 2D drawing. One page is fine. Title block with material, general tolerance, finish and units. Mark only the critical dimensions and datums. Call out threads and any special features.
3. Write the line items. Grade + acceptable substitutes, quantity + repeat volume, surface treatment, inspection/documents, target date, compliance and packaging. One short paragraph.
4. State your assumptions. Units (mm), Incoterms (e.g. FOB or DAP your city), and that quotes should include tooling if any. Stating assumptions is what makes quotes comparable.
5. Send the identical package to each supplier. Same files, same line items, same assumptions. If you tell one supplier the repeat volume and not another, their quotes are no longer comparable.
6. Give a decision date. "Quotes by Friday" sets a clock and tells you who is responsive before you commit a program to them.

What a good RFQ email actually looks like

You don't need a portal or a form. A clear email does the job:

Subject: RFQ — Bracket, 6061-T6, qty 50 (likely 3,000/yr)

Attached: bracket_revB.step and bracket_revB.pdf (drawing).

• Material: 6061-T6. Substitute 6082-T6 acceptable.
• Tolerances: two critical (bore Ø12 H7, top face flatness 0.02) called out on the drawing; general ISO 2768-m.
• Finish: clear anodise, Type II.
• Quantity: 50 now; likely 3,000/year if approved — please flag a tooling path if cheaper at volume.
• Inspection: FAI report + material cert required.
• Need parts by: 20 Aug. Ship DAP Chicago.
• Please quote by Fri and state your assumptions.

That message can be quoted accurately without a single follow-up question. Sendot quotes a package like this within 12 hours of receiving the CAD. You can send the same block to Protolabs, Xometry, Hubs or Fictiv and get numbers that actually line up — because the inputs are identical.

Making quotes comparable across suppliers

Accuracy is one goal; comparability is the other. Three quotes are only comparable if three things are true: every supplier received the same files, the same line items, and the same stated assumptions. Comparability breaks in quiet ways. One supplier quotes ex-works and another quotes delivered, so the cheaper-looking one isn't. One assumed no material cert and priced it out; another included it. One quoted the exact grade; another used a substitute you hadn't authorised. When the numbers come back, put them in a table normalised to the same Incoterm, the same certs and the same grade before you compare. If a quote is far lower, the usual reason is that the supplier left something out — read their assumptions before you celebrate. Who you send the RFQ to matters as much as what's in it; vetting the supplier itself is covered in how to vet an overseas CNC supplier.

Common mistakes that cost you days or money

• Model only, no drawing. Forces the estimator to guess intent. The number-one cause of clarification rounds.
• Tight tolerances everywhere. The biggest avoidable cost. Tolerance the few features that matter, general-class the rest.
• "Aluminium" with no grade. Un-quotable without an assumption; the assumption may be wrong.
• No repeat volume. Supplier prices the wrong process; you overpay now or can't scale.
• Inspection assumed, not stated. FAI and certs you expected aren't in the price, then appear as a surprise.
• Different package to each supplier. Quotes look different because the inputs were different, not the suppliers.
• No Incoterm. You compare an ex-works price against a delivered one and pick wrong.
• Asking about duties from the supplier. Import duty and VAT are yours to determine as importer of record; classify the part yourself using your country's tariff schedule (for the US, the USITC HTS; for the EU, TARIC) or a licensed customs broker. Rates change and must be confirmed at time of import — don't ask a machinist to price your landed cost.

Frequently asked questions

A complete RFQ is the cheapest quality tool you own. It costs twenty minutes and it removes the two things that ruin a sourcing cycle: guesswork and back-and-forth. Assemble the package once, send it unchanged to everyone, and the quotes that come back will be accurate and comparable the first time. When your package is ready, send it to Sendot and we'll return a quote within 12 hours.