When sourcing custom metal parts, an accurate quotation starts with clear technical information. Whether you need CNC machined components, die castings, metal stampings, or sheet metal parts, incomplete specifications can lead to repeated questions, unexpected costs, and production delays.
A well-prepared Request for Quotation (RFQ) helps manufacturers understand exactly what you need, evaluate the right production process, and identify potential manufacturing risks before production begins.
For purchasing managers, engineers, and product developers, this guide explains what to include in an RFQ for custom metal parts and how to make supplier quotations easier to compare.
The engineering drawing is one of the most important documents in a custom manufacturing RFQ.
Whenever possible, provide both a 2D engineering drawing and a 3D CAD model. They serve different purposes:
2D drawing: Communicates dimensions, tolerances, threads, surface finish, material specifications, and inspection requirements.
3D CAD model: Helps the manufacturer understand the component's geometry, features, and overall design.
Revision information: Identifies the approved version to be quoted and manufactured.
Common file formats include PDF for drawings and STEP or STP for 3D models. Other formats may also be acceptable, depending on the manufacturer's software and workflow.
If the drawing and CAD model contain conflicting information, clearly state which document takes precedence. Do not assume the supplier will automatically know which version is correct.
Buyer tip: Include the part number, drawing revision, units of measurement, and date where applicable. If a design changes after quotation, request a review of the affected price, tooling, lead time, and inspection requirements.
A material description such as "aluminum," "stainless steel," or "carbon steel" may not provide enough information for an accurate quotation.
Different grades and conditions can have different mechanical properties, machining behavior, corrosion resistance, and costs.
Your RFQ should identify the following wherever applicable:
Material grade or alloy designation
Temper or heat-treatment condition
Applicable material specification
Required mechanical or chemical properties
Material certification or traceability requirements
Whether alternative materials may be proposed for approval
For example, specifying aluminum 6061-T6 is more informative than simply stating "aluminum." Likewise, stainless steel 304 and 316 should not automatically be treated as interchangeable.
If the material grade has not yet been finalized, explain the component's operating environment and functional requirements. The manufacturer can then assess whether alternative materials are worth considering, subject to your engineering approval.
Tolerances define the permitted variation in a part's dimensions or geometry. They are particularly important when components must fit together, align with other parts, seal against a mating surface, or move within an assembly.
However, tighter tolerances are not automatically better.
More demanding tolerances may require additional machining operations, specialized fixtures, more frequent measurements, or more extensive inspection. Applying unnecessarily tight tolerances to every dimension can increase manufacturing cost without improving the component's actual function.
Before sending your RFQ, identify:
Critical dimensions that affect fit or function
Hole diameters, thread specifications, and hole positions
Flatness, perpendicularity, concentricity-related requirements, or positional controls where applicable
Important mating surfaces and datum references
General tolerances and any special requirements
For drawings using geometric dimensioning and tolerancing (GD&T), identify the applicable standard, such as ASME Y14.5, and ensure that the drawing communicates the intended inspection requirements clearly. ASME describes Y14.5 as a standard for interpreting dimensioning and tolerancing on engineering drawings and digital product definitions. ASME Y14.5 overview.
Buyer tip: Tell the supplier which features are functionally critical. If you are unsure whether a tolerance is necessary, ask for a manufacturability review rather than relaxing or tightening it without engineering justification.
The manufacturing process does not always end when the part comes off the machine or production line.
Surface treatment, deburring, polishing, plating, coating, heat treatment, and assembly can all affect the final product's cost, lead time, and acceptance criteria.
Your RFQ should specify:
Required surface finish or roughness, if applicable
Plating, anodizing, powder coating, painting, or other treatments
Applicable treatment specifications and coating thickness, where required
Color, gloss, or cosmetic appearance requirements
Surfaces that must remain untreated or be protected
Deburring, edge-breaking, cleaning, or assembly requirements
For example, a component may require zinc plating on most surfaces but leave specific contact areas untreated. If these requirements are not shown clearly, the supplier may need to request clarification before quoting.
For appearance-critical parts, identify the visible surfaces and explain what types of scratches, marks, discoloration, or other defects are acceptable.
Quantity has a direct effect on manufacturing planning and quotation structure.
A supplier quoting ten prototype parts may recommend a different process from one quoting thousands of parts per year. Tooling investment, setup time, automation, material utilization, and inspection arrangements can all influence the cost structure.
Include the following information:
| Information | What to provide |
|---|---|
| Initial order quantity | The quantity you expect to purchase now |
| Expected annual demand | A realistic estimate of future requirements |
| Repeat order pattern | Whether orders are regular, seasonal, or project-based |
| Sample requirements | Whether prototypes or pre-production samples are needed |
| Delivery schedule | Required date and any planned shipment stages |
If your expected quantity is uncertain, ask for quotations at several quantities, such as 100, 500, and 1,000 pieces, where those levels make sense for the project.
This allows you to evaluate how the unit price changes with production volume without committing to an unconfirmed forecast.
Inspection requirements should be agreed upon before production, not introduced unexpectedly after the parts are completed.
Tell the manufacturer what evidence you need to verify that the supplied parts meet your specifications.
Depending on the application, requirements may include:
Certificate of Conformity (CoC)
Material test certificate or material report
Dimensional inspection report
First Article Inspection (FAI)
Hardness or mechanical test reports
Special testing or traceability records
Customer-specific inspection forms
Not every part requires every document. The correct inspection plan depends on the component's function, risks, drawing requirements, and customer quality system.
For example, a bracket with several mounting holes may require verification of hole position and overall dimensions. A component used in a pressure-containing assembly may require additional testing specified by the design authority.
Buyer tip: Identify the critical-to-function dimensions and required documents in the original RFQ. Also clarify the acceptance criteria and any special inspection method that must be used.
A technically correct component can still create problems if it arrives damaged, contaminated, or later than required.
For custom metal parts, packaging may need to prevent scratches, corrosion, deformation, or part-to-part contact during transport.
Include relevant requirements such as:
Individual protection or separators between parts
Rust prevention or moisture protection
Special cleanliness or contamination controls
Labeling, part numbers, and lot identification
Carton or pallet requirements
Delivery destination and preferred shipping terms
Required arrival date or staged delivery schedule
If the parts are cosmetic, precision-finished, or sensitive to contamination, explain this before quotation so that the supplier can account for the required protection.
Two quotations may look similar but cover different deliverables. Before comparing prices, confirm what is included.
Check whether the quotation covers:
Raw material and manufacturing
Tooling, molds, fixtures, or setup charges
Secondary processing and assembly
Inspection and documentation
Packaging
Freight or other delivery costs
Sample approval and production release
If tooling is required, ask whether it is charged separately, how it will be maintained, and what arrangements apply to ownership and future use.
Also specify your target delivery date, destination, requested quotation currency, and any applicable purchasing terms. This helps suppliers quote against the same scope rather than making assumptions that may later cause disputes.
One of the easiest ways to create confusion is to send a revised drawing without clearly identifying what changed.
For each RFQ, maintain a controlled set of documents with matching part numbers and revision identifiers. If you issue a new revision, tell the supplier whether it replaces the previous version and request confirmation of any impact on the quotation.
For repeat orders, confirm that the drawing revision on the purchase order matches the approved production documents.
This simple practice helps prevent suppliers from quoting one design and manufacturing another.
Before sending your next inquiry, use this checklist to confirm that the essential information is available.
Current 2D drawing with dimensions and tolerances
3D CAD model, where available
Part number and drawing revision
Material grade and condition
Critical dimensions and inspection requirements
Surface finish and secondary processing
Initial order quantity and expected annual demand
Sample or first-article requirements
Required certificates and reports
Packaging and delivery requirements
Tooling scope and commercial terms
Target delivery date and destination
If some information is not yet available, identify it as pending rather than leaving the supplier to guess.
You can use the following structure when contacting a custom parts manufacturer.
Subject: RFQ – Custom Metal Part – [Part Number]
Dear Sales Team,
Please find attached the engineering drawing and CAD model for our custom metal part.
Could you please review the requirements and provide a quotation based on the following information?
Part number and revision: [Insert details]
Material and condition: [Insert specification]
Surface treatment: [Insert requirements]
Initial order quantity: [Insert quantity]
Expected annual demand: [Insert estimate, if available]
Inspection and documentation: [Insert requirements]
Required delivery date: [Insert date]
Shipping destination: [Insert destination]
Please identify any technical questions, recommended design adjustments, or quotation assumptions that require our confirmation.
If possible, please provide a breakdown of tooling or setup charges, unit pricing at the requested quantities, and estimated lead time.
Thank you. We look forward to your quotation.
Best regards,
[Your Name]
[Company Name]
A complete RFQ does more than help you obtain a price. It gives the manufacturer the information needed to evaluate manufacturability, identify risks, plan inspection, and quote the correct scope of work.
For buyers sourcing custom CNC machined parts, die castings, metal stampings, or other precision components, the most important step is to communicate the actual requirements clearly before production begins.
At CPRMFG, we work with customers on custom manufacturing projects based on engineering drawings and specifications. If you have a new component to source, send us your drawing, material requirements, quantities, and target delivery date for a quotation review.
Contact CPRMFG to discuss your custom metal parts project and request a quote.
Whenever possible, provide a 2D engineering drawing and a 3D CAD model, along with the material, quantity, finish, tolerances, and delivery requirements. Identify the current revision and clarify which document controls if the files conflict.
Yes, an initial budgetary discussion may be possible with a sketch, sample, or preliminary model. However, missing dimensions, materials, or acceptance requirements may prevent the supplier from providing a firm production quotation. Confirm the remaining technical details before placing the order.
No. Tolerances should reflect the part's function and assembly requirements. Unnecessarily tight tolerances can increase manufacturing and inspection costs without delivering a practical benefit.
Yes, if you have a reasonable estimate. Expected future demand helps the manufacturer evaluate whether tooling, process planning, or alternative production arrangements may be appropriate. Clearly distinguish forecasts from committed orders.
Confirm that each quotation covers the same material, revision, tolerances, surface treatment, quantity, inspection documents, packaging, tooling, delivery terms, and lead time. A lower unit price may not represent a lower total project cost if important items are excluded.
You can submit your drawing and project requirements for review. The feasibility of the part, production route, tolerances, and delivery schedule should be confirmed against the specific design and order requirements.
