A good CNC quote begins before the inquiry is sent. If the documentation is complete, the supplier can assess the process, setup cost, cycle time and risks faster. If the drawing is ambiguous, quoting turns into a series of questions: what material, what tolerance, does the surface need grinding, how many pieces, is this a prototype or a batch.
At Nomatec, the smoothest quotes are for projects where the design engineer or buyer sends the full package: PDF drawing, STEP model, quantity and process requirements. If the documentation is not ready yet, you can start with a consultation via contact, but it is worth knowing what will be missing for an accurate quote.
The minimum set for a quote
The best starter package is:
- a technical drawing in PDF,
- a 3D model in STEP,
- material or a range of acceptable materials,
- quantity: prototype, small batch, repeat production,
- expected deadline,
- finish information: surface roughness, anodising, zinc plating, passivation, painting,
- quality control and measurement requirements.
If the part requires CNC turning and CNC milling, a 3D model greatly helps assess the number of setups and the sequence of operations. For simple shafts a PDF drawing is often enough for a preliminary quote, but for housings, pockets, undercuts and multi-operation parts a STEP model shortens the analysis.
What must be on the drawing?
A technical drawing should answer the question: what really matters for the part's function. Not every dimension needs a tight tolerance. In practice the most important elements are mating surfaces, bearing seats, fitted holes, threads, mounting hole patterns and datums.
| Documentation element | Why it is needed | What happens when it is missing |
|---|---|---|
| Tolerances on critical dimensions | Selecting the process and inspection time | A quote based on assumptions, or follow-up questions |
| Material | Selecting tools, parameters and supply | Price drift as early as material purchasing |
| Quantity | Spreading the setup cost across the batch | The unit price may be over- or understated |
| Surface roughness | Assessing finishing operations | Underestimated grinding or extra passes |
| Inspection requirements | Measurement time and quality documentation | Measurement cost missing from the offer |
If you are not sure which tolerances are necessary, flag it in the inquiry. Often a variant can be proposed: functional tolerances only on working surfaces, with the rest to standard shop tolerances.
PDF, STEP, DXF - which file to send?
PDF is good for requirements but weaker for assessing geometry. STEP is good for geometry but usually carries no complete information on tolerances and surface roughness. DXF or DWG are useful for cut, flat parts, simple plates and 2D contours.
The safest set:
- PDF as the requirements document,
- STEP as the 3D geometry,
- DXF/DWG if the part has a significant 2D contour,
- an email note with the quantity, deadline and the part's purpose.
If the project is still a concept, technical design and CAD/CAM can help. The model, datums, tolerances and design-for-manufacturing simplifications can then be refined before the actual production quote.
The most common mistakes in inquiries
No quantity
The price of one piece and the price of a batch of 100 are two different worlds. Setup, programming, tool preparation and first-article inspection have to be spread over something. So state at least: prototype, initial batch and potential repeats.
The same tolerance everywhere
A tolerance of ±0.01 mm across the whole part sounds precise, but it is often unnecessary and expensive. It is better to point out the critical surfaces. The rest can follow standard production tolerances.
Unclear material
"Steel" is not enough. C45, S355, 1.4301 and 42CrMo4 mean different prices, availability and machining parameters. If the material is not fixed, write: "C45 preferred, substitute possible after consultation".
No information about the application
This is not about revealing project secrets. Context is enough: sliding bushing, clamping element, test part, machine component, drive shaft. This information helps select the process and point out risks.
Decision box: is the documentation ready?
Use a short check before sending the inquiry:
| Question | If the answer is "no" |
|---|---|
| Do I know the material? | Ask for a material variant or selection for the load case |
| Do I know the quantity? | Give at least a range: 1, 10, 50, 100+ |
| Are the critical tolerances marked? | Mark the functional surfaces and fits |
| Is there a 3D model? | For complex geometry, prepare a STEP |
| Is a surface finish required? | Add the coating, roughness or a note saying "no coating" |
How to send a good inquiry?
In the body of the message, briefly state:
- what the part is,
- how many pieces the inquiry covers,
- whether production is one-off or repeat,
- the expected deadline,
- which requirements are critical,
- whether you allow a change of material or process.
Example: "Please quote 25 pcs of bushings in C45 per the PDF and STEP. The internal H7 diameters and Ra 1.6 surface are critical. A repeat batch of 50 pcs per quarter is possible. Expected lead time: 3 weeks."
Summary
Complete documentation does not mean a long description. It means clear data: PDF, STEP, material, quantity, tolerances and deadline. The fewer assumptions the supplier has to make, the faster you get a reliable quote.
If you want to check whether your documentation is sufficient for a quote, send your project to Nomatec. For parts requiring machining, we can tell you right away whether turning, milling, a documentation change or a technical consultation stage is the better path.
FAQ
Is a 3D model alone enough for a CNC quote?
A 3D model helps assess the geometry, but it usually does not replace a PDF drawing with tolerances, surface roughness and inspection requirements. It is best to send both files.
Which file formats are most convenient for quoting?
The safest set is PDF for the drawing and STEP for the 3D model. DXF or DWG can also help for flat parts and 2D documentation.
Does missing tolerance information block a quote?
Not always, but it increases the risk of assumptions on the supplier's side. For fitted surfaces, threads, holes and working diameters, tolerances should be stated explicitly.
What has the biggest impact on quoting speed?
Complete documentation, a clear quantity, the material, surface requirements and information about which dimensions are critical. Without this data, follow-up questions are needed.
Can Nomatec help prepare the documentation?
Yes. If the documentation is conceptual or incomplete, the Nomatec team can help organise the requirements before quoting and production.
Related topics
How much does a CNC machined part cost and what drives the price?
A practical breakdown of CNC part pricing: material, programming, setup, cycle time, tolerances, inspection and batch size.
Read the articleC45 steel, stainless or aluminium — how to choose the material for a part?
Choosing the material for a CNC part without guessing: when to pick C45, when stainless steel and when aluminium.
Read the articleCNC turning vs. conventional turning — when does each pay off?
We compare two turning technologies. When does CNC come out cheaper, and when is a conventional lathe the only sensible choice? Real numbers, zero marketing.
Read the articleTolerances in CNC machining — how much does accuracy cost?
Why tight tolerances raise the cost of a CNC part and how to specify accuracy so you pay only for the critical dimensions — general tolerances, fits, IT grades and surface roughness.
Read the articleHow to choose a CNC machining company?
What really matters when choosing a CNC supplier: matched technology, quality control and tolerances, a transparent quote, lead times and red flags.
Read the article