Custom Metal Parts RFQ Checklist: What Buyers Should Include

Direct answer: A useful RFQ for custom metal parts should identify the current drawing revision, part function, material specification, critical dimensions and tolerances, expected quantity, manufacturing or process constraints, finish requirements, inspection and documentation needs, packaging expectations, and the requested project timing. When these inputs are clear, an engineering team can review manufacturability, identify open questions, and prepare a more reliable quotation.

This checklist helps buyers sourcing cast, forged, stamped, die-cast, or CNC-machined components reduce clarification cycles before sampling. It does not replace a controlled drawing or an engineering review.

1. Start with controlled part identification

Identify exactly what is being quoted. Include the part name, part number, drawing number, and revision. For an assembly, add a file list or bill of materials.

• Part name and part number

• Drawing number and revision level

• Drawing issue date

• 3D model and 2D drawing, when available

• Assembly relationship or bill of materials, when applicable

• Clear statement identifying which file controls if the model and drawing differ

Do not send an updated model under an old file name without a change note. See Engineering Drawing Revision Control for OEM Metal Parts.

2. Explain the part function and service conditions

A drawing may not explain why a feature matters. State the part function and known load, wear, corrosion, temperature, sealing, mating, appearance, safety, or assembly conditions. Use only approved engineering requirements.

3. Define the material requirement precisely

State the material grade and governing standard instead of a broad description such as "steel" or "aluminum." If equivalents may be considered, define who can approve them.

• Material grade and applicable standard

• Required mechanical or chemical properties, if not fully defined by the standard

• Heat treatment condition, when required

• Restrictions on substitutions or recycled content, when applicable

• Material certificate or certificate of conformity requirements

If the process is open, the supplier can review metal casting, die casting, forging, stamping, or CNC machining. Final selection requires part-specific review.

4. Separate critical tolerances from general tolerances

Identify dimensions affecting fit, sealing, alignment, motion, or assembly. Avoid assigning the same tight tolerance to every dimension. Mark critical characteristics and datums clearly.

• General dimensional tolerance standard

• Critical dimensions and geometric tolerances

• Datum scheme and measurement reference

• Surface roughness on functional areas

• Threads, fits, sealing faces, and machining allowances

• Any dimensions that must be checked at first article, in process, or final inspection

5. Give realistic quantity and demand information

Quantity affects tooling, process choice, planning, packaging, and price assumptions. Give the immediate quantity and expected demand pattern.

• Prototype or sample quantity

• Initial production order quantity

• Estimated annual usage

• Expected batch size or release frequency

• Program duration, if known

• Whether the quotation should separate tooling, samples, and production parts

6. State finish and secondary-operation requirements

List heat treatment, coating, plating, painting, passivation, deburring, marking, cleaning, assembly, or other secondary operations. Reference the applicable specification and approved cosmetic standard.

7. Define inspection and documentation deliverables

Agree inspection requirements before quotation. Castle's published process describes first article, in-production, and pre-shipment inspection, with inspection reports and certificate-of-conformity support. PPAP and CPK documents can be discussed when required. State the exact submission and approval process.

• First article inspection scope and approval responsibility

• In-process and final inspection requirements

• Sampling plan or 100% inspection requirements for selected features

• Material certificates and certificate of conformity

• PPAP, capability, or other customer-specific documents, when required

• Retention period and delivery format for inspection records

Review Castle's published quality control information and state any project-specific additions in the RFQ.

8. Include packaging, logistics, and commercial assumptions

State corrosion protection, cosmetic-surface separation, package weight, labeling, barcode, pallet, and export-packing needs. Add delivery location, currency, Incoterm if applicable, and freight assumptions.

9. Provide a target schedule with approval gates

List the quotation date, engineering review window, sample target, first article approval period, and production target. This exposes dependencies such as drawing, tooling, material, or document approval.

Compact RFQ package checklist

Frequently asked questions

What files should be included in a machining RFQ?

Include a controlled 2D drawing, a matching 3D model when available, the drawing revision, material specification, critical tolerances, surface-finish requirements, quantity, inspection requirements, and any required secondary processes. State which file controls if the model and drawing conflict.

What should be added to a casting RFQ?

In addition to the standard RFQ inputs, identify the required material grade, expected quantity, functional surfaces, machining allowances or finished dimensions, heat treatment and finish requirements, inspection needs, and whether the manufacturing process is fixed or open to engineering review. See How to Choose the Right Metal Casting Process for OEM Parts.

Should buyers specify every tolerance as tightly as possible?

No. Tolerances should reflect functional and assembly needs. Clearly distinguish critical characteristics from general dimensions so that manufacturing and inspection plans focus on what matters to the part.

When should PPAP or capability data be requested?

Request them when they are required by the customer, industry, program, or risk plan. Define the required level, characteristics, format, and approval responsibility in the RFQ so the supplier can include the work in its review and quotation.

Can a supplier quote from a sample without a drawing?

A sample can support an initial discussion, but missing design authority, material definition, tolerances, and acceptance criteria create uncertainty. Buyers should establish an approved drawing or other controlled technical definition before production requirements are finalized.

Send a reviewable RFQ package

A complete RFQ should be controlled, specific, and clear about what remains open for engineering review. Send controlled drawings and requirements through the Castle Mechanical contact page.