Last updated on September 2nd, 2026 at 01:34 pm
A 3D CAD model and drawing tell a sheet metal fabricator a lot about a part, but they may not contain every requirement that applies to the order.
Customer specification documents can define company-wide requirements for materials, hardware, finishing, workmanship, inspection, documentation, packaging, and other details that apply in addition to the individual part drawing.
Whether you are an OEM, contract manufacturer, job shop, mechanical engineer, or buyer sourcing precision sheet metal parts, providing these requirements before quoting helps your fabricator understand the complete scope of the job.
What Are Customer Specification Documents?
Customer specification documents establish requirements that may apply across multiple parts, assemblies, purchase orders, or suppliers.
Depending on the organization, these documents may be called internal specifications, workmanship standards, supplier quality requirements, manufacturing specifications, engineering standards, or another company-specific name.
They can contain requirements covering:
| Requirement | Examples |
|---|---|
| Materials | Approved alloys, tempers, substitutions, and material certification requirements |
| Hardware | Approved manufacturers, exact part numbers, installation requirements, and allowable substitutions |
| Welding | Weld requirements, cosmetic expectations, workmanship, and inspection requirements |
| Finishing | Powder coating, anodizing, plating, chromate conversion coating, color, masking, and appearance requirements |
| Workmanship | Deburring, edge condition, scratches, handling marks, cosmetic surfaces, and weld blending |
| Inspection | Critical dimensions, dimensional reports, first article inspection, sampling, and other inspection requirements |
| Documentation | Certificates of conformance, material certifications, outside process certifications, and traceability requirements |
| Identification | Part marking, labels, serialization, and other identification requirements |
| Packaging | Protective film, wrapping, part separation, labeling, and other packaging requirements |
Some companies maintain detailed specification packages covering many different manufacturing situations, while others use a smaller set of design and supplier requirements.
What matters is identifying which requirements actually apply to the specific part or order.
Drawing vs. Customer Specification: What’s the Difference?
A custom sheet metal project may be controlled by several different sources of information, including:
- 3D CAD model
- Part drawing
- Assembly drawing
- Purchase order
- Customer specification documents
- Referenced industry specifications
- Approved supplier or process requirements
- Inspection and documentation requirements
The 3D model primarily communicates geometry, while the drawing typically communicates requirements such as dimensions, tolerances, material, finish, hardware, and other part-specific information.
Customer specifications can add requirements that apply beyond the individual drawing.
For example, a drawing might specify a powder coat color while a separate customer specification defines the acceptable gloss, texture, masking, surface preparation, cosmetic requirements, and approved coating products.
The fabricator needs access to all applicable requirements to accurately evaluate the job.
Why Customer Specifications Matter During Quoting
Customer requirements should be supplied with the RFQ whenever possible, not after the order has already entered production.
A requirement discovered after quoting can change the manufacturing process, outside services, inspection requirements, documentation, cost, or lead time.
Examples include previously unidentified requirements for:
- First article inspection
- Dimensional inspection reports
- Material certifications
- Outside process certifications
- Special masking
- Specific plating or coating specifications
- Approved hardware manufacturers
- Serialization or part marking
- Special packaging
- Traceability
- Additional inspection or documentation
Providing these requirements during quoting allows the estimator to evaluate the complete manufacturing and quality requirements rather than discovering additional operations after the price and delivery expectations have already been established.
Finishing and Workmanship Requirements
Finishing and workmanship are areas where customer specifications can be particularly valuable because not every expectation can be communicated by basic part geometry.
Customer specifications may define requirements for:
- Edge condition: Requirements for deburring, edge breaks, or other intentionally controlled edge conditions.
- Cosmetic surfaces: Identification of visible surfaces and acceptable requirements for scratches, handling marks, grinding, weld blending, and other appearance characteristics.
- Directional finishes: Required orientation for brushed or otherwise directional cosmetic finishes.
- Material grain direction: Rolling direction requirements where they are important to forming or part performance.
- Masking: Surfaces, holes, threads, or electrical contact areas that must remain free of coating.
- Coating requirements: Color, gloss, texture, chemistry, specification, or approved coating product where applicable.
- Weld appearance: Requirements for as-welded, ground, blended, or other specified cosmetic conditions.
It is important to distinguish between material grain direction and the direction of a cosmetic brushed finish. Both can matter, but for different reasons.
When these requirements are not defined, the fabricator may apply its normal workmanship practices, which may differ from the customer’s functional or cosmetic expectations.
Material and Hardware Specifications
Customer specifications can also establish approved materials and hardware across a family of products.
Material requirements may define:
- Approved alloy and temper
- Permitted material substitutions
- Material certification requirements
- Traceability requirements
- Restrictions on alternate materials
Hardware specifications may identify approved manufacturers, exact part numbers, installation requirements, or whether substitutions are permitted.
This is particularly important for self-clinching hardware because the exact fastener family affects mounting-hole diameter, minimum sheet thickness, material hardness requirements, edge distance, and installation requirements.
If the customer requires a particular material or hardware part number, that requirement should be identified before the fabricator selects or purchases material and components.
Inspection, Certification, and Documentation Requirements
Not every order requires the same inspection or documentation package.
Depending on the project, customer specifications may require:
- Certificate of Conformance (CoC)
- Material certifications
- Outside process certifications
- Dimensional inspection reports
- First article inspection
- Specific inspection characteristics
- Part or lot traceability
- Customer-specific quality forms
These requirements can add inspection, administrative, or supplier-management work to an order, so they should be identified during quoting.
Packaging, Labeling, and Part Identification Matter Too
Manufacturing requirements do not necessarily end when the part passes inspection.
Customer specifications may also define how finished parts must be protected, packaged, identified, and shipped.
Requirements can include:
- Protective film on cosmetic surfaces
- Individual wrapping or part separation
- Special packaging materials
- Part-number labels
- Lot identification
- Serialization
- Part marking
- Package labeling
These requirements should be included in the RFQ when they affect the work required to deliver the finished product.
What Happens When Requirements Conflict?
Multiple documents can sometimes contain requirements that appear to conflict.
For example, a drawing may call out one finish while a customer specification references another, or a purchase order may reference a different revision of a specification than the drawing.
The fabricator should not guess which requirement takes precedence.
When requirements conflict or are unclear, the discrepancy should be resolved with the customer before production. If the customer maintains a formal order of precedence between drawings, specifications, purchase orders, and other documents, that requirement should also be communicated to the supplier.
Always Identify the Specification Revision
Customer specifications change over time as materials, processes, suppliers, quality requirements, and company standards evolve.
Instead of simply stating “use our standard workmanship specification,” identify the applicable document number and revision whenever possible.
For example:
Customer Workmanship Specification ABC-123, Rev. D
This gives the customer and fabricator a specific requirement set to reference during quoting, manufacturing, inspection, and future repeat orders.
If you are supplying a specification that has been used for several years, confirm that it is still the current revision before sending it to your fabricator.
Older drawings and internal standards sometimes reference materials, hardware, coatings, or specifications that are no longer readily available or have been superseded.
If a fabricator identifies an obsolete or unavailable requirement, the appropriate replacement should be clarified with the customer.
A newer revision, similar material, alternate hardware part number, or apparently equivalent finishing process should not automatically be substituted when the customer has explicitly specified something else.
Depending on the requirement, customer approval may be necessary before an alternative can be used.
Best Practices for Sharing Customer Specification Documents
Getting the correct requirements to your sheet metal fabricator does not need to be complicated.
- Identify which documents actually apply. Avoid sending a large collection of corporate specifications without indicating which ones govern the part or order. Clearly identify the applicable documents and requirements.
- Include document numbers and revisions. This helps everyone confirm that the same version is being used.
- Find the owner of technical requirements. If the buyer does not have the applicable specifications, determine who does. Depending on the organization, that may be engineering, manufacturing engineering, quality, supplier quality, or another group.
- Share requirements during the RFQ process. Do not wait until after the quote or purchase order if a requirement could affect manufacturing, inspection, documentation, cost, or lead time.
- Identify proprietary or controlled information. Some specifications contain proprietary technical or quality information. Follow the customer’s required process for sharing and controlling those documents with suppliers.
- Communicate revisions. If a specification changes, make sure the fabricator receives the new revision and understands when it becomes applicable.
What to Send With Your Sheet Metal RFQ
A complete RFQ package helps your fabricator evaluate both the geometry of the part and the requirements surrounding it.
Whenever applicable, provide:
- 3D CAD model
- Fully dimensioned 2D drawing
- Material and thickness
- Order quantity
- Applicable customer specification numbers and revisions
- Finish specification
- Hardware manufacturer and part numbers
- Weld requirements
- Critical tolerances and GD&T
- Inspection requirements
- Certification and documentation requirements
- Packaging and labeling requirements
- Assembly requirements
- Any other applicable customer or industry specifications
If you have applicable customer documents, sharing them at the beginning of the project helps our team review those requirements along with your CAD files and drawings.
Give Your Fabricator the Complete Requirement Set
A manufacturable CAD model is only one part of a successful custom sheet metal project. The fabricator also needs to understand the material, tolerances, hardware, finishing, workmanship, inspection, documentation, packaging, and other requirements that apply to the finished product.
The earlier those requirements are identified, the more accurately the fabricator can evaluate manufacturability, price, lead time, inspection, and documentation.
Ready to discuss your next prototype or low-volume sheet metal project? Request a quote and send us your 3D model, drawing, and applicable customer specifications.
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Metal Fabrication Internal Specification Documents FAQ
What are internal specification documents, and why are they crucial for precision sheet metal jobs?
Internal specification documents outline requirements, protocols, and expectations regarding hardware, materials, finishing, quality control, and certifications for a specific project. They’re vital as they provide detailed guidance beyond the RFQ, helping fabricators ensure precise adherence to unique project needs.
How can I obtain internal specification documents from customers for a precision sheet metal job?
It’s often beneficial to ask engineers directly for these documents rather than buyers. Clearly explain the necessity of these documents, emphasizing confidentiality and how they aid in meeting precise project requirements. Regularly check for updates, as specifications can change with evolving technologies and materials.
Companies may guard internal specifications due to confidentiality concerns or may not recognize their importance in the fabrication process. By explaining the necessity and assuring confidentiality, you can often overcome these barriers.
How often should I check for updates in internal specification documents provided by customers?
Internal specifications can change over time due to evolving technologies and requirements. Regular communication with the customer contact helps stay updated. If documents are outdated, confirm with the customer to ensure the most current information is available for the fabrication process.
How do internal specification documents benefit both the fabricator and the job shop outsourcing the project?
Detailed internal specification documents assist fabricators in producing parts precisely to customer requirements. This ensures efficient fabrication, meeting customer expectations, and fostering confidence in the job shop’s ability to deliver accurately, enhancing their reputation with clients.