Last Updated: March 2026
How to Get a CNC Machining Quote: What to Include for Fast, Accurate Pricing
To get an accurate CNC machining quote from Rapid Manufacturing, you need: a STEP file (3D CAD), a material specification (grade-level, e.g., "6061-T6 Aluminium"), a surface finish requirement, and your required quantity. A 2D drawing is strongly recommended if your part has tight tolerances, GD&T callouts, or specific thread requirements. With these four items, Rapid Manufacturing will return a binding quote within 2 business days.
RFQ Checklist
- ✓3D CAD file in STEP format (.stp or .step)Required
- ○2D drawing in PDF (for GD&T, tight tolerances, or thread specs)Recommended
- ✓Material specification (grade, e.g., "Aluminium 6061-T6")Required
- ✓Surface finish requirement (e.g., "As-machined Ra 1.6µm" or "Type II Anodised")Required
- ✓Quantity requiredRequired
- ○Delivery date or required lead timeRecommended
- ○Any applicable certifications required (ISO 13485, AS9100-D, material certs)Recommended
- ○NDA required? (all Rapid Manufacturing suppliers operate under NDA by default)Recommended
File Format Guide
The file format you submit significantly affects the accuracy of your quote and the quality of machining.
STEP (.stp, .step)PreferredUniversal 3D CAD format. Preserves exact geometry, dimensions, and feature definitions. All major CAD packages (SolidWorks, Fusion 360, CATIA, NX, Inventor) can export to STEP. All CAM software can import it. Use this format.
IGES (.igs, .iges)AcceptedOlder but widely compatible neutral format. Slightly less reliable than STEP for complex geometry but generally acceptable for quoting purposes.
Native CAD (SolidWorks .sldprt, Fusion 360, etc.)AcceptedNative files from common packages are acceptable but may require conversion. STEP export from your CAD tool is preferred.
STL (.stl)Not suitable for CNCSTL is a mesh format designed for 3D printing. It loses geometric precision and cannot represent exact dimensions. Do not submit STL files for CNC machining quotes.
PDF DrawingRequired for tight tolerancesSubmit a 2D drawing in PDF alongside your STEP file if your part has critical tolerances, GD&T, thread specs, or surface finish requirements on specific surfaces.
How to Specify Tolerances
Good tolerance specification saves time and money. Here's how to do it correctly:
- Use a general tolerance block
Put a general tolerance in your title block: e.g., "Linear dimensions: ±0.1mm unless otherwise specified". This sets the default for non-critical dimensions.
- Callout only critical tolerances explicitly
Use GD&T or explicit ±xx callouts only for dimensions that are functionally critical — mating surfaces, bearing seats, sealing faces. This focuses machining effort and cost where it matters.
- Specify standard tolerances (±0.05mm) as the default
Rapid Manufacturing achieves ±0.05mm as standard across most features. Specify ±0.01mm or tighter only where truly necessary — it significantly increases cost.
- Match tolerances to function
A clearance fit for a pin through a hole might only need ±0.1mm. A precision bearing seat needs ±0.01–0.02mm. Design each tolerance to its function.
Surface Finish Specifications
| Finish | Ra Value | Typical Use |
|---|---|---|
| As-machined | Ra 1.6–3.2µm | General structural parts, most prototype work |
| Fine machined | Ra 0.8µm | Mating surfaces, sliding interfaces |
| Bead blasted | Ra 1.6–3.2µm | Cosmetic finish, uniform appearance |
| Type II Anodised (aluminium) | Ra 1.0–2.0µm | Corrosion protection, cosmetic, electrical insulation |
| Type III Hard Anodised (aluminium) | Ra 1.0–2.0µm | Wear resistance, hardness up to 70 HRC surface |
| Powder coated | Ra 2.0–5.0µm | Robust cosmetic finish, colour options |
| Electroless nickel | Ra 0.5–1.0µm | Wear and corrosion resistance, uniform thickness |
| Passivation (stainless) | No change | Remove free iron, maximise corrosion resistance |
Common Mistakes That Delay Quotes
- ✗Submitting an STL file instead of a STEP file
- ✗Specifying material as "aluminium" or "stainless" without a grade — this requires a clarification email that delays your quote
- ✗No tolerance specification — we default to ±0.1mm but you may need tighter
- ✗Contradictions between the 3D model and 2D drawing — always check that the drawing matches the model
- ✗Omitting thread specifications — thread standard (Metric, UNC, UNF), class of fit, and depth must be specified
- ✗Not stating whether cosmetic surfaces need special treatment — if visible surfaces matter, say so
Rapid Manufacturing's Quoting Process
- 1Submit filesDay 0
Upload your STEP file and drawing via the quote form. Include material, quantity, and surface finish requirements.
- 2DFM reviewDay 1
Our engineering team reviews your design for manufacturability issues, flag anything that may affect quality or cost, and prepares the RFQ for our supplier network.
- 3Quote returnedDay 1–2
You receive a detailed quote with itemised pricing, lead time options, and any DFM recommendations. No hidden fees.
- 4Quote approvalDay 2–3
Review and approve the quote online. Ask questions or request modifications — we'll revise the quote as needed.
- 5ProductionDays 3–17
Parts enter production immediately on payment confirmation. Standard lead time is 7–14 business days for CNC prototypes.
- 6Quality inspection and dispatchBefore shipping
All parts are inspected against your specifications. CMM reports available on request. Parts shipped directly to your door.
Ready to Get a Quote?
Upload your STEP file and receive a detailed quote from Rapid Manufacturing within 2 business days. Free DFM analysis included with every submission.
Submit Your RFQFrequently Asked Questions
What file format should I use for CNC machining quotes?
STEP (.stp or .step) is the preferred format for CNC machining quotes. It is a neutral format that all CAD systems can export and all machining CAM software can import reliably. IGES is also widely accepted. Avoid STL files for CNC quoting — STL is a mesh format designed for 3D printing and loses dimensional accuracy. If you use SolidWorks, Fusion 360, or CATIA, export to STEP before submitting.
Do I need a 2D drawing as well as a 3D CAD file?
A 3D STEP file is sufficient for a budgetary quote. However, for a binding production quote, a 2D drawing is strongly recommended if your part has: (1) tolerances tighter than ±0.1mm that aren't obvious from the model, (2) GD&T callouts (flatness, perpendicularity, true position), (3) specific surface finish requirements on certain surfaces, (4) thread specifications, or (5) any requirements that cannot be communicated in a 3D model alone.
How do I specify tolerances on my CNC drawing?
The most effective approach is to use a general tolerance block on your drawing (e.g., "Unless otherwise specified: linear dimensions ±0.05mm, angular dimensions ±0.5°") and then callout tighter tolerances only on critical dimensions using standard GD&T notation. This keeps the drawing clean while ensuring critical dimensions get the attention they need. Avoid specifying tight tolerances on every dimension — it significantly increases cost without functional benefit.
What surface finish should I specify for CNC machined parts?
For most functional parts, as-machined (Ra 1.6µm) is appropriate and lowest cost. Specify surface finish in Ra (roughness average) values, or use the standard surface finish symbols per ISO 1302. Common callouts: Ra 3.2µm (standard machined), Ra 1.6µm (fine machined), Ra 0.8µm (ground or fine-milled), Ra 0.4µm (precision ground). If you need a specific post-process (anodising, powder coating, passivation), call this out on the drawing as a general note.
How long does Rapid Manufacturing take to provide a CNC quote?
Rapid Manufacturing provides CNC machining quotes within 2 business days of receiving a complete submission (STEP file + drawing if applicable + material specification). For urgent requests, same-day or next-day quoting is available — contact us to arrange.
What happens after I submit my files for a quote?
After you submit, Rapid Manufacturing's engineering team reviews your files and performs a free DFM (Design for Manufacturability) analysis. They check for features that may cause quality issues or increase cost — and will flag these in the quote with suggested modifications. You'll receive a detailed quote within 2 business days covering material, process, finishing options, and lead time. Once you approve and pay, parts enter production immediately.
What commonly causes delays in CNC quoting?
The most common delays are: (1) Missing or vague material specification — "aluminium" without a grade. (2) No 2D drawing to clarify tolerances on complex parts. (3) STL format submitted instead of STEP. (4) Missing surface finish specification. (5) Contradictions between the 3D model and 2D drawing. Providing a complete STEP file, drawing, material grade, and surface finish spec upfront avoids all of these.