Guide
How do you check a CNC machining quote against the drawing before placing the PO?
A CNC machining quote is the supplier’s written offer to make a defined part at a stated price, and it is only as good as the assumptions behind it. To check one, read it line by line against the drawing revision you intend to order and confirm that material, condition, tolerances, finish, threads, inspection, documents and packaging each appear on the quote exactly as the drawing and RFQ state them, or are listed as explicit exclusions you accept.
By Saola Manufacturing engineering team · Published · Updated
The problem shows up after the purchase order, not before it. The cheapest bid wins, the first lot arrives, and the parts are bare when the drawing called for anodize, or made from a free-machining grade when the drawing named a structural alloy, or measured only on a sample basis when your quality plan expected a full report on critical features. The supplier points to its quote, which said “material: aluminum” and “finish: as machined,” and the purchase order quietly referenced that quote. Most pages about quotes stop at how to request one or how to compare prices. This guide is for the buyer and the engineer who sign off on the award: how to spot what a quote left out, how to compare bids on the same basis, and what to write into the PO so the drawing, not the quote, defines the part. It is general purchasing and engineering guidance, not legal advice.
On this page
What does an incomplete CNC machining quote look like?
An incomplete quote prices a part that is easier than the one on your drawing. The usual signs are generic material wording, no mention of finish or heat treatment, no drawing revision, and silence on inspection and documents.
Read the quote as if it were the only document the shop floor will ever see. Red flags include a part number with no revision letter; material written as a family (“stainless,” “aluminum,” “steel”) instead of a grade, temper and specification; a finish line that says “standard” or “as machined” when the drawing calls for a coating; no reference to threads, inserts or hardware; a single price with no breakdown of one-time charges; phrases such as “per our standard tolerances” or “commercial quality”; and an exclusions or notes section that you have not read. A quote that is much lower than the others for the same drawing deserves the closest look, because a gap in scope is a frequent reason for a gap in price.
None of these is necessarily bad faith. Many shops quote from a model, skip the notes on the PDF, or quote what they assume the buyer wants so they can respond quickly. The point of the review is to turn those assumptions into written, agreed terms before money and machine time are committed.
Why do quotes leave out finish, material or tolerances?
Usually one of five things: the supplier quoted from the 3D model and never read the drawing notes, the RFQ itself was ambiguous, the supplier deliberately excluded scope to stay competitive, the quote and the drawing referred to different revisions, or the quote’s own terms were never reconciled with the PO.
- Model-only quoting. Automated and fast-turn quoting often reads geometry from a STEP file. Notes that live only on the 2D drawing, such as finish, heat treatment, thread class, general tolerances and inspection requirements, never reach the price. The STEP file versus 2D drawing guide explains which information the model cannot carry.
- Ambiguous RFQ. “Anodize black” without a type or class, a material named without a standard, or a title block with no general tolerance leaves the supplier free to pick the cheapest reasonable reading. The RFQ package guide covers how to close those gaps at the source.
- Deliberate exclusions. Some suppliers quote the machining only and list finish, inspection reports or packaging as “excluded” or “by others,” expecting to add them later as changes.
- Revision mismatch. The RFQ went out on one revision, engineering released another, and the quote never caught up.
- Battle of the forms. The quote carries its own terms and conditions, the PO carries yours, and nobody reconciles them. For US sales of goods, UCC §2-207 says a definite and seasonable expression of acceptance works as an acceptance even when it states additional or different terms, unless it is expressly conditional on assent to them. Between merchants, the additional terms become part of the contract unless the offer expressly limits acceptance to its own terms, they materially alter it, or an objection is given within a reasonable time.
| Item on the drawing or RFQ | What the quote should state | Common gap |
|---|---|---|
| Part number and revision | Exact number and revision letter quoted | No revision, or an older one |
| Material | Grade, temper or condition, and governing specification | Material family only, or a substituted grade |
| Material documents | Mill test report or material certificate, if required | Not mentioned, or charged extra |
| General tolerances | Title-block or note tolerances accepted as drawn | “Shop standard tolerances” |
| Critical and GD&T callouts | No exceptions, or each exception listed | Silent, then measured loosely |
| Threads and inserts | Thread size and class; inserts and hardware included | Inserts or gauging omitted |
| Surface texture | Roughness callouts accepted | Treated as cosmetic |
| Finish and heat treatment | Process, specification, type or class, color, masking | “As machined” or “finish by others” |
| Edge break and cosmetic notes | Accepted as drawn | Ignored |
| Inspection and reports | First article, sampling, report format | Not included |
| One-time charges | Fixtures, programming, setup shown separately | Buried in the first lot or added later |
| Packaging, marking, origin, Incoterm | Stated against your requirement | Default packing, no origin statement |
How do you check a quote against the drawing, line by line?
Put the drawing, the RFQ and the quote side by side and walk every callout on the drawing to a line on the quote. Anything the quote does not mention is either included at no extra charge, excluded, or unknown, and you need it in writing which one.
A practical method:
- Balloon the drawing. Number every dimension and note, as you would for a ballooned inspection report. Each balloon becomes a line on your review sheet.
- Match the identity. Confirm the part number, revision, quantity breaks and units of measure on the quote match the RFQ. A mismatch here invalidates the rest of the review.
- Walk the notes block first. Material, finish, heat treatment, general tolerances, edge breaks, marking and cleanliness live in the notes, and that is where model-based quotes fail.
- Read the exclusions and assumptions section twice. Then read the supplier’s terms and conditions, including warranty, inspection and acceptance language.
- Ask about every unknown in one written list. One consolidated technical question sheet gets a better answer than a dozen emails. Ask the supplier to confirm “no exceptions to drawing revision X” or to list each exception.
- Record the answers on a revised quote, not only in correspondence, so the document you reference on the PO is complete.
- If the PO is already placed, do not wait for the first lot. Send the gap list to the supplier, ask for a written confirmation or a revised quote against the drawing revision, and issue a PO amendment that adds the missing finish, material specification or inspection requirement before material is bought or the part is machined.
This mirrors the review of customer requirements that quality management system standards already expect of a supplier: review the customer’s requirements, including ones not stated but necessary for the intended use, and resolve any that differ from the inquiry before committing to supply. Asking for a “no exceptions” statement simply makes that review visible to you.
How do you compare several machining quotes on the same basis?
Build a bid tab: one row per scope item from your checklist and one column per supplier, then normalize every bid to the full scope before comparing price. A bid that excludes finish or inspection is not cheaper until you have priced what it leaves out.
US federal buyers use the same logic. Price analysis under FAR 15.404-1(b)(2)(i) lists first, and treats as a preferred technique, the comparison of prices received in response to the solicitation, which only works when the offers cover the same requirement. For custom parts, that means the following decision rules:
- Scope item missing from one bid. Ask that supplier to requote it, or add your own estimate of the missing item to that column, then compare.
- Different material or finish offered. Treat it as a different part. Either the engineer approves the alternative for all bidders, or the alternative bid is set aside.
- One-time charges handled differently. Compare total cost over the expected quantity, with fixtures, programming and first article broken out. The NRE cost guide explains when to pay one-time charges up front and when to spread them.
- Exceptions to tolerances. Send each exception to the design engineer. If an exception is acceptable, release a revised drawing so every supplier quotes it; the cost of tight tolerances guide shows how loosening a non-functional callout can lower the price for every bidder.
- Terms that conflict with your PO terms. Flag warranty, liability, acceptance and inspection clauses for your contracts team before the award, not after a dispute.
Only after the columns are equal does price, communication quality and the supplier’s questions become a fair basis for the award. A supplier that asked good questions about your drawing has usually read it.
What should the PO say so the quote cannot override the drawing?
Name the drawing number and revision as the governing requirement, state an order of precedence in which the drawing outranks the quote, and reference the quote only for price and agreed exceptions. Then require written acknowledgement of the PO.
- Governing documents. “Parts shall conform to drawing 1234, revision C, and all specifications referenced on it.” Add the model file and revision, and say which governs if they disagree.
- Order of precedence. For example: PO, then quality agreement, then drawing, then referenced standards, then supplier quote. State that supplier terms printed on a quote or acknowledgement do not apply unless accepted in writing, and that acceptance is limited to the PO’s terms, which is the situation UCC §2-207 addresses.
- Agreed exceptions only. “Exceptions to the drawing are limited to those listed on quote Q-567, revision 2, and approved by buyer engineering.” Anything else needs a formal deviation request.
- Material and finish restated. Repeat the material specification and the finish specification on the PO line, including type, class, color and masking where they apply, so a sub-supplier sees them too.
- Inspection and documents. List the reports required with the shipment: first article on new parts and revisions, material certificates, finish documentation and any first article inspection format you expect.
- Origin and packaging. Ask for the production site and country of origin, the marking and the packing method in writing.
- Revision changes. Route any later change through an engineering change notice with a requote, never an email edit to the drawing.
If a nonconforming lot still arrives, the written record decides the outcome. In US federal practice, supplies that do not conform in all respects should be rejected, and when a critical or major nonconformance is accepted anyway, the contract is modified for an equitable price reduction or other consideration (FAR 46.407). A commercial buyer has far firmer ground for the same outcome when the PO made the drawing the requirement.
How is a quote reviewed against the drawing on a Saola order?
A Saola quote is written against the drawing and revision you send, lists any exception or question in a short manufacturability note, and names the production site and country of origin for each process.
Saola Manufacturing is the brand of Aximora Global Trading Co., Ltd., a Ho Chi Minh City company that places and manages metal-parts work. CNC milling and CNC turning run at our lead CNC plant, T.K Viet Nam Precision Company Limited. Anodizing, plating, powder coating and other surface finishing, as well as die casting, sand casting and stamping, are done by partner plants we manage. Those partners are not named and are not necessarily in Vietnam, so the quote states where each process runs and the resulting country of origin. That matters for this review: if your drawing calls for a finish, check that the quote shows the finish line and its site, not only the machining.
Read the manufacturability note as the exceptions list described above, answer it on a revised drawing if anything changes, and reference the drawing revision and the quote number on your PO. ISO 9001 certification is in progress, not held, so state the inspection reports you need on the RFQ rather than assuming them. When you are ready, send the drawing, the model and the revision you intend to order through the quote form.
Frequently asked
What should a CNC machining quote include?
At minimum: part number and revision, quantity breaks, unit price, one-time charges shown separately, material grade and condition, finish and heat treatment, any exceptions to the drawing, inspection and documents included, packaging, Incoterm, origin and the validity period of the offer.
Does referencing a supplier quote on my PO make its terms binding?
It can. If the PO says “per quote” without an order of precedence, the quote’s exclusions and terms may become part of the contract. Reference the quote for price and listed exceptions only, and state that the drawing governs.
Why is one machining quote so much lower than the others?
Often it leaves something out: finish, material documents, inspection, one-time charges or a tight callout. Sometimes the supplier simply has a better-suited machine or process. A side-by-side bid tab shows which it is.
What does “no exceptions to the drawing” mean on a quote?
It is the supplier’s statement that it has reviewed every callout and note on the named revision and will make and inspect the part to all of them at the quoted price. Ask for it in writing, with the revision letter.
Should I accept a substitute material offered on a quote?
Only after the design engineer approves it and the drawing or a formal deviation records it. Ask all bidders to quote the same substitute so the comparison stays fair.
Sources
- UCC §2-207, Additional Terms in Acceptance or Confirmation, Legal Information Institute, Cornell Law School, accessed October 2026
- FAR 15.404-1, Proposal Analysis Techniques, Federal Acquisition Regulation (48 CFR), accessed October 2026
- FAR 46.407, Nonconforming Supplies or Services, Federal Acquisition Regulation (48 CFR), accessed October 2026
- ASME Y14.5-2018, Dimensioning and Tolerancing, ASME, 2018 (reaffirmed 2024)
- ISO 2768-1:1989, General tolerances — Tolerances for linear and angular dimensions without individual tolerance indications, International Organization for Standardization, 1989 (confirmed 2022)