Guide
Build to print vs build to spec: who owns the scrap when the drawing is wrong?
Build to print is a supply arrangement in which the buyer owns the design and the supplier makes the part exactly as the released drawing, model and referenced specifications define it, while build to spec means the supplier is given the required function or performance and owns the design choices needed to meet it. When a build-to-print part matches a drawing that turns out to be wrong, the parts are usually conforming and the cost of the bad design generally sits with the drawing owner, unless the supplier ignored an obvious error, built to the wrong revision or the contract moves that risk.
By Saola Manufacturing engineering team · Published · Updated
The problem usually arrives as an argument, not a defect report. A lot of machined or cast parts lands, passes receiving inspection against the drawing, and then will not assemble, leaks, or interferes with a mating part. Engineering says the supplier should have caught it. The supplier says it built exactly what the print said. Purchasing is left holding a scrap tag and two incompatible stories. This guide is for the design engineer, the supplier quality engineer and the buyer who need to settle that argument quickly and stop it from happening again: how responsibility is normally split, how to tell a wrong drawing from a supplier error, what a build-to-print supplier may and should question, and the wording to put on the drawing, RFQ and purchase order. It is general engineering and purchasing guidance, not legal advice; where real money is at stake, your contract and your counsel decide.
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How do you recognize a build-to-print dispute over a wrong drawing?
The signature is a part that measures good to the drawing but fails in the assembly or in use. If the inspection report and the drawing agree and the part still does not work, the problem is in the design definition, not in the manufacturing.
Three patterns cover most cases. In the first, the drawing is plainly wrong: a dimension was mistyped, a hole pattern was mirrored, a thread was called out in the wrong size, or the model and the 2D drawing disagree and the supplier followed one of them. In the second, the drawing is ambiguous: a feature has no tolerance and no general tolerance block applies, a note says “break edges” or “smooth finish” with no value, a datum scheme allows two reasonable setups, or a material is named without a standard or condition. In the third, the drawing is correct but incomplete for the function: every dimension is met, yet nothing on the print captures the sealing face, the fit with a mating part or the cosmetic side that the engineer had in mind.
Each pattern points to a different owner, which is why the first step is not to assign blame but to classify the failure. Ask for the supplier’s inspection results by drawing callout, the revision letter it built to, and any questions it raised at quote or order acknowledgement. Those three records usually decide the case before anyone has to debate it.
Who owns the scrap under build to print versus build to spec?
Under build to print the design owner, usually the buyer, carries the risk that a correct copy of its drawing does not work, and the supplier carries the risk of not matching the drawing. Under build to spec the supplier also carries the risk that its design does not meet the stated function.
The split follows from what each side controls. US federal procurement draws the same line between two kinds of requirement documents. The Defense Standardization Program guide SD-15 defines a detail specification as one that sets design requirements such as the materials, how a requirement is achieved or how the item is fabricated, and notes that detail specifications are sometimes called build-to-print specifications; a performance specification states the required results and the criteria for verifying them without stating the method. In construction law the US Supreme Court held in United States v. Spearin that a contractor required to build to the owner’s plans is not responsible for the consequences of defects in those plans, and that general clauses telling the builder to check the plans do not shift that responsibility. Spearin is a construction and government-contract doctrine and is not automatically applied to a commercial parts purchase, but it illustrates the same allocation: whoever dictates the design carries the risk that the design is wrong.
Commercial sales law points the same way. Under the Uniform Commercial Code, an implied warranty that goods are fit for a particular purpose arises only when the buyer relies on the seller’s skill or judgment to select or furnish suitable goods (UCC §2-315), which is exactly what a buyer does not do when it hands over a complete drawing. Exact or technical specifications also displace an inconsistent sample or general description (UCC §2-317), and, unless otherwise agreed, a buyer who furnishes specifications must hold a merchant seller harmless against infringement claims arising from complying with them (UCC §2-312). On the other side, the buyer may still reject goods that fail to conform to the contract in any respect (UCC §2-601, subject to the installment-contract rule and any agreed limits on remedies), so a supplier that misses a drawing callout owns that miss whatever the design quality.
| Situation | Usual owner of the cost | Why |
|---|---|---|
| Build to print: part misses a drawing callout | Supplier | Nonconforming to the contract; buyer may reject |
| Build to print: part meets a drawing that is wrong | Design owner (buyer) | Supplier was told what to make and made it |
| Obvious error or conflict the supplier saw and did not raise | Often shared, sometimes supplier | A clear discrepancy is expected to be queried before production |
| Hidden ambiguity, supplier picked a reasonable reading | Usually the drawing author | Contra proferentem: an ambiguous term is construed against its drafter |
| Supplier built to a superseded revision | Supplier | Revision control is a supplier obligation once the change is acknowledged |
| Buyer sent or ordered the wrong revision | Buyer | The order defined the requirement |
| Build to spec: part meets the spec but fails the stated function | Supplier | Supplier owned the design choices that deliver the function |
| Build to spec: function was never stated or was changed later | Buyer | The supplier cannot design to a requirement it was not given |
How do you tell a wrong drawing from a supplier error?
Measure the failed parts against the drawing revision on the purchase order, callout by callout, and compare the result with the supplier’s own inspection report. A conforming part that fails function is a design or definition problem; a nonconforming part is a manufacturing problem.
Work through the checklist below in order. It replaces opinion with records.
- Confirm the revision. Compare the revision letter on the PO, on the supplier’s order acknowledgement, on the inspection report and on the parts or tags. A mismatch at this step ends most disputes on the spot.
- Re-measure the failure features. Use a ballooned drawing so every result maps to one callout, and measure the features involved in the failure, not only the ones the supplier reported.
- Check the model against the drawing. If a STEP file was sent, confirm whether the drawing or the PO states which one governs. Drawing preparation and revision follow ASME Y14.100 in many companies; whatever the standard, a model and a drawing that disagree with no note on precedence are a gap in the released definition, and the party that released both owns that gap.
- Look for untoleranced or unstated requirements. Under ASME Y14.5, each dimension needs a tolerance, either directly or through a general note, except dimensions marked as reference, maximum, minimum or stock, and the drawing should define the part without specifying manufacturing methods. A feature with neither is a gap in the definition, not freedom for the supplier to guess wrong.
- Read the paper trail. Find any technical question, deviation request or manufacturability note the supplier sent, and the answer it received.
- Test whether the problem was visible. Give the drawing alone to someone who did not design the part and ask whether the error or conflict can be seen on the page itself, without knowing the assembly. An error visible on the drawing (two views that disagree, a thread that cannot fit the boss it sits in) points toward a supplier that should have asked; an error that only shows in the assembly (a mating part the supplier never saw) points back to the design owner.
- Check the mating parts. If the parts conform and still fail, measure the mating parts and run a tolerance stack-up; the drawing tolerances may simply not close the stack.
Write the outcome as a short finding: conforming or nonconforming, which callout, which revision, and whether the issue was visible on the drawing before production. That finding is what you take into the commercial conversation, and it is the input to a formal corrective action if one is needed.
What should you do with parts that meet a wrong drawing?
Decide disposition on engineering grounds first and commercial grounds second. Choose between use as is, rework, or scrap, correct the drawing through a change notice, and then settle cost according to the finding, not the other way round.
The decision table below is a practical starting point for the material review discussion.
- Function is acceptable as made. Record a use-as-is decision on the lot, and revise the drawing so the next order matches what works. The parts were conforming, so no supplier deviation is needed.
- Reworkable by the supplier. Typical examples are opening a hole, adding a chamfer or re-cutting a thread. Ask the supplier to quote the rework as a change; if the drawing was wrong, rework is normally paid work, not a free correction.
- Not reworkable. Scrap the lot, issue the corrected revision through an engineering change notice, and place the replacement order against the new revision.
- Parts are nonconforming. This is a supplier miss. Reject, return or ask for correction, or accept through a formal deviation with a price adjustment. US federal practice follows the same sequence: nonconforming supplies are normally rejected, the contractor is ordinarily given a chance to correct or replace them within the delivery schedule at no added cost, and when critical or major nonconformances are accepted anyway the contract is modified for an equitable price reduction or other consideration (FAR 46.407).
- Mixed finding. If the supplier saw an obvious conflict and stayed silent, or both sides signed off a first article that already showed the problem, a negotiated split is common. Record the split and the reason so the next dispute does not start from zero.
Whatever the outcome, close the loop on the document. A wrong drawing that is used once becomes a wrong drawing used again by the next supplier, the next buyer and the next revision of the assembly.
What may a build-to-print supplier question, and what should it not change?
A build-to-print supplier should question anything it cannot make or measure as written, anything that conflicts, and anything that looks like an obvious error. It should not change the design on its own authority, even when it is sure it knows better.
Good suppliers raise questions at the quote or order acknowledgement stage, because that is when an answer is cheapest. Fair questions include: two views that give different values for one feature; a model that does not match the drawing; a tolerance tighter than the stated inspection method can resolve; a thread, material or finish callout with no standard or class; a datum that cannot be fixtured as defined; a feature that cannot be reached by any tool; or a dimension that looks like a typing error against the rest of the part. Questions about cost are fair too: a supplier may point out that a looser tolerance or a different radius would cut cost, and the cost of tight tolerances guide shows why that conversation is worth having.
What a supplier must not do is silently “fix” the drawing. If it moves a hole it thinks is wrong, opens a tolerance or substitutes a material, it has taken over design responsibility for that feature without the authority or the information to carry it, and it may have broken a fit it cannot see. The correct route is a written question, a written answer, and either a drawing revision or a formal deviation. The buyer’s side of the bargain is to answer quickly and in writing, because an answer given on a phone call is an answer nobody can find when the dispute starts.
What should the drawing, RFQ and purchase order say so the dispute does not recur?
State which kind of work it is, which documents govern and in what order, and how questions and changes are handled. Most build-to-print disputes come from a purchase order that left all three unstated.
- Type of work. “Build to print. Buyer retains design authority. Supplier is responsible for conformance to the drawing and referenced specifications.” For build to spec, list the functional requirements and the verification test, and say which design decisions the supplier owns.
- Governing documents and revision. Name the drawing number and revision, the model file and its revision, and state which governs if they disagree, for example “Drawing governs; model is for reference except where the drawing states otherwise.”
- Order of precedence. PO, then quality agreement, then drawing, then referenced standards, or whatever order suits you, but write it down. For warranties, UCC §2-317 lets the parties’ intention decide which one dominates when they cannot be read as consistent; a written order of precedence states that intention for every document on the order instead of leaving it to be argued later.
- General tolerances and units. A title block or note that covers every untoleranced dimension, and the edition of the dimensioning standard used, so no feature is left open. The standard machining tolerances guide covers what happens when this is missing.
- Duty to query. “Supplier shall report in writing any conflict, ambiguity or apparent error in the technical data before starting production, and shall not proceed on the affected features until answered.”
- No unauthorized change. “Any departure from the drawing requires a written deviation or a revised drawing from the buyer.”
- First article. Require a first article inspection on new parts and new revisions, and do an assembly trial with it; a wrong drawing caught at first article costs one part instead of a lot.
- Critical features. Mark the characteristics that carry function, so both sides know where a question matters most.
Write these clauses once into a standing quality agreement or PO terms, then reference them on every order. Repeating them part by part invites the version on one PO to drift from the version on the next.
How is build-to-print work handled on a Saola order?
Orders quoted from your drawing are build-to-print work: the drawing and revision named on the purchase order define what is made and checked. Questions about conflicts or unclear callouts are raised in writing with the quote, so they are answered before production starts.
Saola Manufacturing is the brand of Aximora Global Trading Co., Ltd., a Ho Chi Minh City company that places and manages metal-parts work. Machined parts are made by CNC milling and CNC turning at our lead CNC plant, T.K Viet Nam Precision Company Limited. Die casting, sand casting, stamping and surface finishing are done by partner plants we manage, which are not named and are not necessarily in Vietnam; each quote states the production site and the country of origin. On a cast-and-machined part that usually means two plants work to one drawing, so the drawing has to be explicit about which features are as-cast and which are machined, as the casting versus machining drawing guide explains.
The quote comes with a short manufacturability note. Treat it as the place where questions about your drawing appear: a conflict between model and drawing, a callout without a standard, a feature we cannot measure as written. Answer them on the drawing, not only in an email, and send the revised drawing with the order. If you want a supplier to own part of the design, such as a casting draft or a fixturing feature, say so on the RFQ so it is quoted as design work rather than assumed. ISO 9001 certification is in progress, not held. To start, send the drawing, model and the revision you intend to order through the quote form.
Frequently asked
What does build to print mean?
It means the supplier makes the part exactly to the buyer’s released drawing, model and referenced specifications, without changing the design. The buyer keeps design authority and the supplier is responsible for matching the documents.
Is the supplier responsible if it builds exactly to a wrong drawing?
Usually not for the design error itself, because the parts conform to what was ordered. The picture changes if the error was obvious and the supplier said nothing, if the supplier built to the wrong revision, or if the contract assigns design review to the supplier.
What is the difference between build to print and build to spec?
Build to print hands over the design and asks for an exact copy. Build to spec hands over the required function, performance and interfaces and asks the supplier to design the part to meet them, so the supplier also owns whether the design works.
Who should pay to rework parts made to a wrong drawing?
Usually the drawing owner pays, because rework of conforming parts is a change to the order, unless the contract says otherwise or the supplier ignored an obvious error. Agree the price before the rework starts, and issue a revised drawing so the next lot is made to the corrected design.
Does a signed first article transfer responsibility to the buyer?
It records that the measured features met the drawing at that point, which strengthens the case that later lots built the same way are conforming. It does not excuse a later lot that drifts out of tolerance, and it does not prove the design works unless the first article was also tried in the assembly.
Sources
- United States v. Spearin, 248 U.S. 132, U.S. Supreme Court, 1918 (via U.S. Government Publishing Office)
- UCC §2-315, Implied Warranty: Fitness for Particular Purpose, Legal Information Institute, Cornell Law School, accessed October 2026
- UCC §2-317, Cumulation and Conflict of Warranties Express or Implied, Legal Information Institute, Cornell Law School, accessed October 2026
- UCC §2-312, Warranty of Title and Against Infringement, Legal Information Institute, Cornell Law School, accessed October 2026
- UCC §2-601, Buyer’s Rights on Improper Delivery, Legal Information Institute, Cornell Law School, accessed October 2026
- FAR 46.407, Nonconforming Supplies or Services, Federal Acquisition Regulation (48 CFR), accessed October 2026
- SD-15, Guide for Performance Specifications, Defense Standardization Program, 2009
- ASME Y14.5-2018 (R2024), Dimensioning and Tolerancing, ASME, 2018
- ASME Y14.100-2017, Engineering Drawing Practices, ASME, accessed October 2026
- Contra proferentem, Wex legal dictionary, Legal Information Institute, Cornell Law School, accessed October 2026