How to prepare a CNC machining RFQ

A machining RFQ does not need to be long, but it should remove ambiguity. The goal is to let each supplier price the same part, quantity, material and quality requirements. When key information is missing, the supplier must either ask follow-up questions or make assumptions that can change cost and lead time.

Start with a 3D model and controlled 2D drawing

A STEP file is commonly useful for geometry and CAM preparation. A 2D PDF drawing should control the information that a model alone cannot communicate clearly, including tolerances, threads, surface finish, datums, inspection notes and any dimensions that are critical to function.

Make sure the drawing and model use the same revision. Include a part number, revision identifier and units on the drawing and in the RFQ filename.

Specify material precisely

“Aluminum” or “stainless steel” is usually too broad. Name the grade and, where relevant, condition or temper—for example, aluminum 6061-T6 or a specified stainless grade. If substitutes are acceptable, say which performance requirements must remain equivalent and ask the supplier to identify the proposed alternative.

Separate prototype and production quantities

List the quantity required now and any expected repeat volume. Setup, programming, workholding and inspection effort are distributed differently across one prototype, a batch of 20 and recurring production. Requesting quantity breaks can make those differences visible.

Call out only the tolerances that matter

Mark critical dimensions, fits, datum relationships and inspection characteristics. Apply a sensible general tolerance to noncritical dimensions. Requiring tight tolerances everywhere can increase setup, inspection and scrap risk without improving how the assembly works.

Define threads, edges and surface finish

• Identify thread standard, size, class and depth.
• State whether sharp edges must be broken, chamfered or radiused.
• Give roughness requirements only on surfaces where they matter.
• Specify anodizing, plating, powder coating, passivation or other finish, including color or applicable standard when required.
• Clarify whether dimensions apply before or after coating.

Describe inspection and documentation

Tell the supplier whether you need a standard dimensional check, first-article report, material certificate, coating certificate, measurement records or pre-shipment photos. Identify the exact characteristics that require recorded results. Documentation that appears late in the process can cause delay or require work to be repeated.

Include delivery and commercial details

State the delivery country, required arrival date, preferred shipping method and whether the quote should include freight. Add packaging, labeling, batch separation or hardware-kitting requirements when they affect the delivered condition.

A clear RFQ does not guarantee that every feature is manufacturable as drawn, but it gives the supplier enough information to identify questions early and return a quotation with fewer hidden assumptions.