KEY TAKEAWAYS

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Always include a fully dimensioned drawing alongside your 3D model — the drawing controls, the model informs.

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Specify tolerances explicitly; never assume the supplier will default to what you need.

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Material callout must include alloy, temper, and any required certifications — not just a common name.

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Surface finish, plating, and post-processing requirements belong in the RFQ, not in a follow-up email.

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Quantity, target price, and delivery expectations upfront — these directly shape how a shop quotes the job.

Most quote delays and pricing surprises trace back to a single root cause: an incomplete RFQ. A supplier quoting from a 3D model with no drawing, no tolerance callouts, and a one-line description is essentially estimating — not quoting. That estimate will either be padded for risk or dangerously optimistic. Neither outcome serves you.

A well-structured RFQ forces you to resolve ambiguity before it becomes a manufacturing defect or a change order. It also compresses the back-and-forth communication that eats program schedules. When a supplier has everything they need in the initial package, they can quote accurately, plan toolpaths intelligently, and flag real DFM concerns rather than guessing at intent.

Think of the RFQ as a contract for communication. The more precisely it documents what you need, the more leverage you have to hold a supplier to that standard — and the more confidently you can compare competing quotes on an apples-to-apples basis. Vague RFQs produce vague quotes, and vague quotes produce budget surprises at the worst possible moment.

Rule of thumb: if a machinist could interpret your drawing two different ways, they will pick the one that is easier to machine — which may not be the one you intended.

Your 3D CAD model is a starting point, not a complete specification. Always accompany it with a fully dimensioned 2D engineering drawing in PDF format. The drawing is the legally binding document that defines the part; the model is a geometric reference. Suppliers quote to drawings. If there is a conflict between the two, the drawing wins — and your RFQ should say so explicitly.

The drawing must include:

• All critical dimensions with tolerances explicitly called out
• GD&T callouts where applicable, using ASME Y14.5 standard
• Surface finish symbols on all relevant faces
• Title block with part number, revision level, material, and finish
• Any view-specific notes — thread specs, counterbore depths, press-fit requirements

Revision control matters more than most engineers acknowledge at the RFQ stage. If you are sending Rev B, say so clearly, and make sure your file names match. Suppliers working from stale revisions is a surprisingly common source of scrap. Include a revision history block on the drawing itself, even if it is only one line deep.

Always send a STEP or IGES file for 3D geometry alongside your PDF drawing — it enables faster DFM review and more accurate toolpath simulation, especially for complex 5-axis geometry.

Writing ‘aluminum’ on your RFQ is not a material callout. A proper material specification includes the alloy designation, temper, and the applicable standard. For example: Aluminum 6061-T651 per AMS 2770 or Stainless Steel 316L per ASTM A276. The difference between 6061-T6 and 6061-T651 matters when your part has tight flatness requirements — stress-relieved plate behaves differently under cutting loads than extruded bar stock.

If your application has regulatory or traceability requirements — aerospace, defense, medical — specify that material certifications (certs) are required with delivery. Most reputable shops can provide mill certs on request, but they need to know upfront to procure from certified material sources. Asking for certs after the fact often means a machine shop has to re-source material and re-run the job.

For ITAR-controlled programs, material traceability is not optional — it is a compliance requirement. Nimble’s certified partner network operates under AS9100 and ITAR registration, so traceability documentation is built into the process, but the material specification still needs to originate in your RFQ. Do not leave it to assumption.

Default machining tolerances — typically plus or minus 0.005 inches for machined dimensions — are adequate for non-critical geometry. They are not adequate for bearing bores, mating surfaces, press-fit features, or anything that must align with a mating assembly. If you need tighter tolerances, call them out explicitly on the drawing and flag them in the RFQ text as critical dimensions.

Critical features deserve special treatment in your RFQ package. Consider adding a Critical Features Table — a simple table listing each critical dimension, its nominal value, tolerance band, and the inspection method required. This tells the supplier exactly where to focus their process controls and makes first-article inspection (FAI) planning straightforward. It also makes it immediately obvious if a tolerance is pushing into jig-grind or EDM territory, which has direct cost and lead time implications.

GD&T flatness, perpendicularity, and true position callouts are frequently misunderstood or ignored when they appear only on drawings without being flagged in the RFQ. Highlight them in your cover note. If your part has a true position requirement of 0.003 inches on a bolt pattern, that is a CMM inspection requirement — the supplier needs to know that before pricing the job, not after the parts arrive.

Warning: Unnecessarily tight tolerances are one of the single largest drivers of machining cost. If a dimension does not functionally require a tight tolerance, do not call one out. Every feature tighter than plus or minus 0.001 inch requires dedicated process attention and adds cycle time.

Surface finish is not decoration — it is an engineering specification. Define it using Ra values (roughness average) with the appropriate units and measurement standard. A callout of Ra 32 microinch (0.8 micrometers) is unambiguous. ‘Smooth finish’ is not. Match your surface finish callouts to functional requirements: sealing surfaces typically require Ra 32 or better, cosmetic faces often allow Ra 125, and internal channels for fluid flow may require Ra 16 or tighter.

Post-processing and finishing operations must be included in the RFQ, not mentioned as an afterthought. Common finishing requirements to specify include:

• Anodizing — Type I, II, or III (hard coat), with color and thickness if applicable
• Electroless nickel plating — thickness range and hardness if required
• Passivation — ASTM A967 or AMS 2700 callout for stainless steel parts
• Chromate conversion coating (Alodine) — Class 1A or 3
• Heat treatment — process spec, hardness range, and whether pre- or post-machining

Finishing operations affect final dimensions. Hard anodize adds 0.0005 to 0.001 inch per surface — if you have a tight bore tolerance, the machinist needs to know the coating goes inside that bore so they can machine undersize to net final dimension. These details must live in the RFQ package.

If your part requires both tight tolerances and a surface coating, always specify whether critical dimensions are pre-coat or post-coat. This single clarification prevents the majority of plating-related rework disputes.

Quantity has a non-linear effect on unit price for machined parts. Setup cost is largely fixed — a 5-axis setup might take two hours regardless of whether you are running 1 part or 50. That setup amortizes over every piece in the run. Provide your target quantity clearly, and if you have anticipated future volumes, mention them. A supplier pricing a 10-piece prototype order who knows a 500-piece production order follows will price more competitively and assign better capacity.

Delivery requirements must be specific. ‘ASAP’ is not a lead time. State your required ship date, whether you need it expedited, and how you want to handle partial shipments if the order is large. If your program has a hard integration date, say so — it tells the supplier your flexibility threshold and helps them decide whether to accept the order given their current workload.

Include target price or budget range if you have one. This is not showing your cards — it is a useful data point. A supplier who knows you are targeting $180 per piece for a complex aluminum housing will immediately flag whether that is feasible or whether there is a design change that could get you there. Hiding your budget wastes everyone’s time when the quote comes back at $340. At Nimble, 24-hour quotes are standard, but the quality and usefulness of that turnaround depends entirely on the completeness of the package you submit.

If your quality requirements are not in the RFQ, you cannot enforce them on delivery. Standard quality documentation for machined parts typically includes a dimensional inspection report, but there is significant variation in what suppliers provide by default versus what they charge as an add-on. Specify what you need upfront.

Common inspection and quality requirements to address in your RFQ:

• First Article Inspection (FAI) per AS9102 — specify full balloon drawing required
• CMM inspection report — identify which features require CMM vs. hand gauging
• Certificate of Conformance (CoC) — should reference drawing number and revision
• Material certifications — mill certs with heat and lot number traceability
• Special process certs — plating, heat treat, NDT (non-destructive testing) as applicable

For aerospace and defense programs, AS9100 certification of your supply chain is not optional. Nimble’s certified partner network carries AS9100 Rev D certification, which means FAI, CoC documentation, and CMM inspection reports are standard deliverables — not extras. If you are sourcing through a non-certified shop for flight-critical parts, you are carrying program risk that no amount of incoming inspection fully mitigates. Build the right quality tier into the RFQ from day one.

A Certificate of Conformance is not an inspection report. A CoC states that parts were made to the drawing; an inspection report proves it with measured data. For critical applications, require both.

Every RFQ package should include a brief cover note — not a form letter, but a concise technical summary that tells the supplier the most important facts about the job before they open a single file. One well-written paragraph can prevent three rounds of clarifying emails.

A strong RFQ cover note includes:

• Part name, part number, and revision
• Material and finish summary
• Quantity requested and any planned production volumes
• Required delivery date or lead time
• Any critical features, tight tolerances, or special processes that require attention
• Quality documentation required (FAI, CMM report, certs)
• Point of contact and preferred communication method

End the cover note with a specific question if you have one — ‘Please flag any DFM concerns that would affect cost or lead time’ is more useful than a generic ‘let me know if you have questions.’ Good suppliers will engage with a direct invitation to provide DFM feedback. That feedback is genuinely valuable: a free DFM review during the quoting stage can catch features that add significant cost for no functional reason, and catching them before machining starts is orders of magnitude cheaper than discovering them in inspection.

Treat DFM feedback from a supplier as signal, not criticism. A shop that flags a 0.002 inch tolerance on a non-functional chamfer is trying to save you money. Listen to it.

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