QuotedPartAnswers · Updated 2026-10-30
The drawing and the 3D model don't match: which one do I quote?
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Ask the customer in writing which governs, and quote the one the paperwork says governs; if nothing says, quote the drawing for tolerances, notes and finish and the model for geometry, list the difference on the quote, and keep the question open. Never quietly choose the cheaper reading. Many mismatches are a revision problem (the model is one revision behind or ahead), and those are fixed by one email.
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Look for an order of precedence
Check three places before you write to anyone. First, the drawing: a note such as "if there is a conflict between this drawing and the model, the model governs," or the opposite. Second, the PO and its terms or the customer's quality clauses, which often list documents in order of precedence. Third, the RFQ email. If any of these says which controls, follow it and note it on your quote.
If the drawing says the model governs, dimensions on the drawing may be reference only; if the drawing governs, the model is a convenience. Without a statement, a common rule of thumb in shops is that the drawing carries the tolerances, finish, material and notes, and the model carries the shape. That rule is not a law, so don't depend on it when the difference matters.
Find out what kind of difference it is
Compare the two before you ask. The kind of difference tells you how to ask and how much it could change the price.
| Difference | Likely cause | What to do |
|---|---|---|
| Revision letter on the drawing differs from the model's | One file is older | Ask for the current pair; don't quote until you know |
| A dimension differs by a small amount | Rounded model, or a drawing edit not carried over | Quote the drawing; note the difference; ask |
| Features on the model aren't on the drawing (or the reverse) | Incomplete update, or a feature added late | Ask; the price may differ by a setup |
| Model is a different material or thickness | Model reused from another part | Quote the drawing's material; ask |
| Tolerances are much tighter on the model or in the notes | Different conventions or a typo | Ask which; price the tighter one as an option |
| Thread, hole or fit callouts differ | Standards or units mixed | Ask; the wrong one is a scrapped lot |
Email and quote wording
"Before we price this: the PDF (rev C) and the STEP file (rev B) differ. The drawing shows a 0.500 in bore and the model shows 0.625 in; the model also has a 0.25 in chamfer the drawing doesn't mention. Please confirm which governs. Until we hear from you we'll quote rev C of the drawing and list the model differences as exclusions."
On the quote itself: "Quoted to drawing 1042 rev C. The supplied model (rev B) differs in the bore diameter and the chamfer; not included. A change to the model's version will be re-quoted." That line costs nothing and settles most later arguments.
Keep the thread. If the customer says by phone that the model governs, send a short email: "Confirming our call: the STEP file governs." A shop that made parts to the wrong source with no written confirmation usually carries the cost of the scrap.
Sources and limits
Claims are dated where they can change. Product calculations are examples from the stated inputs, not a promise about a customer's quote. Competitor wording is attributed to the source shown.
- The precedence rule of thumb and the mismatch table are shop practice, not a standard; check the customer's documents. No statistic is claimed.
Questions
Can I just quote both and let them choose?
You can, as options, if the difference changes the price. Label each clearly and say which one you would make by default.
What if they don't answer?
Quote the drawing, list the model differences as exclusions, and do not start the job until they confirm.
Price one of your own parts
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