The CNC RFQ Checklist: What to Send So Quotes Come Back Comparable

You send the same STEP file to five suppliers. Three quotes come back at 12 to 14 per part FOB Shenzhen, one at 9.80 DDP Chicago, and one at 27 with a note asking for the drawing. The five numbers describe five different scopes, and comparing them is not analysis, it is guesswork with a spreadsheet.

The quality of a CNC quote is set before the supplier sees the part. A complete RFQ takes an extra twenty minutes to assemble and saves days of back-and-forth, several rounds of re-quoting, and the risk of awarding to a supplier who priced a different job.

Why quotes come back incomparable

Four variables account for most of the spread on the same part: scope of finish, scope of inspection, tolerance interpretation, and delivery terms. One supplier quotes machined only while another includes anodize and masking. One quotes a certificate of conformance while another quotes a first article with a full layout. A title block that says "±0.1" next to thirty dimensions at ±0.02 is read differently by every shop. And EXW, FOB and DDP are not three ways of saying the same number.

Fix those four and the remaining spread reflects real differences in capability.

The drawing and model package

Send both a PDF drawing and a 3D model in STEP AP214 or Parasolid. The drawing is controlling; the model is what the CAM programmer uses. If they disagree, the drawing wins, and the disagreement should be resolved before the order rather than at first article.

The drawing needs a single revision letter on every sheet with a revision block; units stated explicitly in the title block or a note, because mixed metric and imperial drawings cause real errors; a complete title block with material, finish, part number and scale; and all views and sections needed to define features that the model alone leaves ambiguous, particularly thread callouts and surface finish symbols. Without a drawing, tolerance, finish, material and marking stay undefined, and the supplier will either guess or quote the most expensive plausible reading.

Tolerance and finish callouts

Tolerance is the largest single driver of unit price after material, and the item most often left to the title block. Specify the general tolerance standard and class, for example ISO 2768-m, or the equivalent block stating linear and angular tolerances by size range; the GD&T standard in use, ASME Y14.5 or ISO 1101, because the two interpret some symbols differently; a datum reference frame that reflects how the part is located in assembly, on surfaces that can be fixtured; the critical characteristics, so the shop knows where to spend effort; and the inspection requirement that follows from them.

A drawing with a stated general tolerance and five marked critical dimensions is cheaper to make and cheaper to inspect than the same part with every dimension toleranced individually. If you have a tolerance stack-up, include the result: it tells the supplier which dimensions carry the function.

Material needs more precision than "aluminum" or "stainless." Write the alloy and condition — 6061-T6, 7075-T651, 316L, 17-4PH in H1025, Ti-6Al-4V — add the stock form if it matters, and state whether mill certificates are required. If a material has a long mill lead time, say whether an equivalent is acceptable; that one sentence can save six weeks.

Finish needs the same treatment. A callout should name the process, the specification, the thickness range and the masking requirement: anodize Type II or III with class and colour, plating with thickness and post-treatment, powder coat with colour reference and gloss, passivation to ASTM A967, bead blasting or polishing with the faces it applies to. Masking is the detail that gets forgotten. Threads, bores, mating faces and grounding points usually need to be bare, every masked area is manual labour, and if the drawing does not say, the supplier will assume the easy case and the parts will not assemble.

Quantities and commercial terms

Give three numbers rather than one: the quantity you need now, the quantity you expect annually, and the quantity at which you would like a price break. A supplier quoting 50 pieces and 2,000 pieces is quoting two different processes, and knowing both helps them propose the better one.

Also state whether the order will repeat and roughly how often, since that affects fixture investment; the delivery schedule, including whether partial shipments are acceptable; and whether samples or a first article are required before the balance ships.

Then the terms that most often force a re-quote. Name the Incoterm and the place: "FOB Shenzhen", "DAP Rotterdam", "DDP Chicago duty paid". A term without a place is not a term. State the currency and whether the price holds for 30 days or floats with the metal index, and give payment terms, typically 30% deposit with the balance against the bill of lading. If you have a target price, include it with a reason: a credible target tells the supplier whether to propose a design change, while an unreasonably low one ends the conversation. State your need-by date rather than accepting whatever is offered.

The checklist

What to do with the replies

Compare line by line before comparing totals. Check that every supplier quoted the same Incoterm, the same finish scope and the same inspection level. If one came back 30% below the others, ask what they excluded rather than assuming efficiency.

Then ask each supplier two questions: which features drive the cost, and what would change if you relaxed a specific tolerance or switched material. The answers separate the shops that quoted from a rate card from the ones that read the part.

At JSHS, quotes come back within 24 hours with a DFM note that names the cost drivers and prices the alternatives, because the fastest quote is the one you do not have to send back. Send the package using this checklist and the reply will follow the same structure, so it compares cleanly against the others.

Frequently asked questions

Can a supplier quote from a STEP file alone?

They can, but the quote will rest on assumptions about tolerance, finish and material that you will only discover when the parts arrive. A one-page drawing with a tolerance block and a finish callout removes most of that risk.

What file formats are best?

PDF for the drawing and STEP AP214 for the model are the most widely accepted, and native CAD files are rarely necessary for quoting.

How many suppliers should I send an RFQ to?

Three is usually enough to establish a market price without spending a week managing replies. More than five rarely improves the outcome.

Should I include a target price?

If it is based on a real benchmark, yes. It tells the supplier whether your expectation comes from a different process, material or volume.