Most CNC machining RFQs arrive as an email with a part name, a quantity, and an attached model. That is enough to get a number back, and not enough to get a number you can trust. A shop receiving an incomplete package either asks questions and delays, or makes assumptions and hides them inside the price.
A well-built RFQ is not longer, it is more specific.
What a CNC Machining RFQ Has to Answer
A complete CNC machining RFQ answers five things: geometry, material and finish, quantity and timing, inspection requirement, and commercial terms. Each changes the process route a supplier prices, so a package covering four out of five does not produce a cheaper quote — it produces a wider spread between the quotes you receive.
The test is whether two suppliers could read your RFQ and plan genuinely different process routes without either of them being unreasonable. If they could, the RFQ is incomplete: add the missing constraint rather than answering clarification emails for a week.
Documents: The Difference Between a Quote and a Guess
Send a STEP or Parasolid model for geometry, and a 2D drawing for everything a model cannot express: dimensions with tolerances, datum callouts, thread specifications, finish notes, and any note that overrides the model. Where the model and the drawing disagree, state which one governs; those conflicts are a recurring source of rework, as covered in STEP file versus 2D drawing: resolving conflicting part requirements.
If no drawing exists, say so and name the features that carry function: a machined face that seals, locates or slides is not interchangeable with one that is merely visible. For drafting conventions machine shops read without guesswork, see how to prepare a 2D drawing for CNC machining.
Material, Condition, and Finish
"Aluminum" and "stainless" are categories, not specifications. Alloy and temper change machinability, strength and anodizing response; grade changes cutting behavior and corrosion performance. State the alloy and condition — 6061-T6 rather than 6061 — or state the functional requirement and let the supplier propose a grade, with substitution subject to written approval.
For finishing, say which surfaces are cosmetic, which are functional, and which may be left as machined; a blanket instruction to anodize everything hides the masking decisions that drive cost. Finishing often happens outside the machine shop, so specify the finish and its acceptance criteria rather than the process — with supplier-coordinated finishing, the specification you write is what travels with the parts.
Quantity, Batch Plan, and Repeat Demand
Give a quantity, a batch plan, and an honest view of repeat demand. One order of 500 pieces and five orders of 100 pieces are different jobs: the first amortizes a single setup across the lot, the second repeats setup, first-piece verification and documentation five times. If the part will run for years, say so, because it changes whether the supplier proposes a dedicated fixture or a general-purpose vise setup.
State whether partial shipments are acceptable, whether quantity is firm or subject to revision, and the date the parts are needed on your dock. "Urgent" is not a date.
Inspection and Documentation Requirements
Say what you will do with the parts when they arrive, and what you expect to receive with them. If you will measure incoming parts against the drawing, name the features you will check. If you need a dimensional report, first article inspection, or material certificates in the shipment, put those in the RFQ; requesting them after the order is placed turns documented scope into a change order.
State the acceptance basis as well: a part that must satisfy every drawing dimension is a different inspection job from one where only flagged critical features are verified, a split discussed in how to compare CNC machining suppliers beyond piece price. If the RFQ is silent, each supplier assumes a different inspection depth.
Commercial Terms That Move the Number
Delivery terms, packaging and payment sit inside the quoted price whether or not they are itemized: incoterms decide who pays freight and where risk transfers, and packaging matters when the part is cosmetic, thin-walled, or carries a face that can be bruised in transit.
Ask for the quotation to state what is included: material certification, finishing, inspection documentation, packaging, freight, and any setup or tooling charge treated separately from the piece rate. A price that buries setup inside the piece rate cannot be compared with one that lists it, and the same is true of scope assumptions — see why CNC machining quotes vary between suppliers.
What Buyers Commonly Leave Out
Three omissions account for most of the spread between quotations:
- Tolerance intent. A drawing that puts a tight tolerance on every dimension is not the same request as one flagging three critical features.
- The governing revision. A model exported before the last drawing change gets quoted as the current design, and the error surfaces at inspection rather than at quotation.
- The finishing scope. Finishes applied to all surfaces, including those masked later, get paid for twice.
None of these is a technical problem. Each is a documentation problem, and each is free to fix before the RFQ goes out.
An RFQ Checklist Before You Send
- Neutral CAD model (STEP or Parasolid) plus a 2D drawing with the governing revision marked
- Alloy and temper, or grade, with substitution rules stated
- Critical features and their tolerances, matched to function
- Surface finish by area, plus the finishing specification and its acceptance criteria
- Quantity, batch plan, and required-on-dock date
- Inspection depth and documentation required with the shipment
- Delivery terms, packaging expectations, and tooling or setup charged separately
If a supplier still returns questions after a package built this way, that says more about the supplier than about your RFQ. Quoted lead time depends on material availability, quantity, process route and inspection requirements. An RFQ that answers these questions does not automatically produce a lower price; it produces quotes that can be compared line by line, which is what allows a sourcing decision to be defended later.