When you send a request for quote to a CNC machine shop, the information you provide directly affects the accuracy of the quote and how quickly you receive it. An incomplete RFQ often leads to back-and-forth questions, delays, and quotes that may not reflect your actual requirements. From a machine shop’s perspective, a well-prepared RFQ allows us to evaluate your project thoroughly, identify potential manufacturing challenges early, and provide pricing that reflects the real scope of work.
This article explains what information you should include in a CNC machining RFQ and why each element matters to the quoting process.
Engineering Drawings
The engineering drawing typically serves as the controlling specification for your part. It communicates dimensions, tolerances, geometric dimensioning and tolerancing (GD&T) callouts, material specifications, and finish requirements in a standardized format that machinists understand.
A complete drawing should include:
- All critical dimensions with appropriate tolerances
- GD&T callouts where applicable
- Material specification
- Surface finish requirements
- Notes about special processes or requirements
- Drawing revision level and date
When the drawing is clear and complete, the machine shop can quote your job with confidence. Ambiguous or incomplete drawings lead to assumptions that may not match your intent, resulting in quotes that don’t reflect the actual work required or parts that don’t meet your expectations.
CAD Files
While the drawing is the controlling document, providing CAD files alongside your drawings offers significant advantages. CAD files allow the machine shop to import your geometry directly into CAM software, reducing programming time and eliminating potential transcription errors from manually recreating your part.
Common CAD formats include:
- STEP (.stp or .step)
- IGES (.igs or .iges)
- Parasolid (.x_t or .x_b)
- Native CAD files (SolidWorks, Inventor, etc.)
STEP files are generally preferred because they’re widely compatible and maintain accurate geometry. When you provide both a drawing and a CAD file, make sure they match. If there’s a discrepancy, the drawing typically takes precedence as the controlling specification, but clarifying any differences upfront prevents confusion.
Material Specification
Material selection affects machining time, tooling requirements, and raw material cost. Be as specific as possible when specifying material. Instead of just “aluminum,” specify the alloy such as 6061-T6 or 7075-T651. Instead of “stainless steel,” indicate whether you need 303, 304, 316, or another grade.
Different alloys within the same material family have different machining characteristics:
- 6061 aluminum machines easily and is cost-effective
- 7075 aluminum is stronger but more expensive
- 303 stainless steel is free-machining
- 316 stainless steel offers better corrosion resistance but is harder to machine
If you’re flexible on material or open to suggestions based on your application requirements, mention that in your RFQ. Sometimes a machine shop can recommend an alternative that meets your performance needs while reducing cost or lead time.
Quantity
Quantity significantly impacts how a machine shop approaches your job. The setup time for a CNC machine is often substantial relative to the time spent cutting parts. For small quantities, setup time represents a larger percentage of the total job cost. For larger production runs, setup cost is amortized across many parts, reducing the per-piece price.
When requesting a quote, specify:
- The immediate quantity you need
- Whether this is a one-time order or potential repeat business
- Expected order frequency if repeat orders are likely
- Whether you need pricing for multiple quantity breaks
Prototype Versus Production Considerations
The distinction between prototype and production quantities affects quoting and manufacturing approach. Prototype work often involves tighter collaboration, potential design feedback, and the understanding that changes may occur. Production work typically assumes a locked design and focuses on repeatability and efficiency.
If you’re ordering prototype parts with the intention of moving to production volumes later, communicate that upfront. The machine shop can consider manufacturing approaches that scale well and provide guidance on design features that may be cost-effective at production volumes but expensive for prototypes.
Tolerances
Tolerances define the acceptable variation in your part dimensions. Tighter tolerances require more careful machining, additional inspection, and often specialized equipment, all of which increase cost.
Many drawings include a general tolerance block that applies to dimensions without specific tolerances called out. Common general tolerance standards include:
- ±0.005″ for fractional dimensions
- ±0.010″ for decimal dimensions with two places
- ±0.005″ for decimal dimensions with three places
When a dimension requires tighter control, call it out specifically on the drawing. If you’re unsure what tolerance is actually needed for your application, consider discussing it with the machine shop. Specifying tighter tolerances than necessary increases cost without adding functional value.
Surface Finish Requirements
Surface finish affects both the appearance and function of machined parts. Finish requirements should be specified on your drawing using standard notation such as Ra values (arithmetic average roughness) measured in microinches.
Common machined finishes include:
- 125 Ra: Standard machined finish, visible tool marks
- 63 Ra: Improved finish, less visible tool marks
- 32 Ra: Smooth finish, often achieved with additional operations
- 16 Ra or better: Very smooth finish requiring grinding, polishing, or specialized processes
If your part requires secondary finishing operations such as anodizing, plating, powder coating, or passivation, include that information in your RFQ. Some machine shops offer these services in-house or through established partners. Others may machine the part only, leaving secondary operations to you.
Required Completion Date
Lead time requirements affect scheduling and sometimes manufacturing approach. A realistic timeline allows the machine shop to schedule your job efficiently alongside other work. Rush jobs may be possible but often carry premium pricing because they disrupt normal scheduling.
When specifying your required date, consider:
- When you actually need the parts, not just when you’d like them
- Whether your timeline includes shipping time
- Any flexibility you have in the schedule
- Whether partial shipments are acceptable if that helps meet your timeline
If you have a firm deadline driven by a customer commitment or project milestone, communicate that clearly. If your timeline is flexible, mentioning that gives the machine shop more scheduling options, which may reduce cost.
Inspection Requirements
Inspection requirements define how the machine shop verifies that finished parts meet specifications. Standard inspection typically includes verification of critical dimensions and features using precision measuring equipment.
Your RFQ should clarify if you need:
- Standard inspection (verification of dimensions on the drawing)
- First article inspection report (detailed documentation of the first part produced)
- Inspection reports for every part or every batch
- Specific inspection methods or equipment
- Compliance with particular standards (which would be your requirement to specify)
Some customers require inspection reports that document specific measurements, inspection methods, and traceability information. If your project requires this level of documentation, include those requirements in your initial RFQ so the machine shop can account for the additional inspection and documentation time.
Special Notes and Requirements
Every project has unique aspects that may not be fully captured in drawings and specifications. Use the notes section of your RFQ to communicate:
- Critical features or dimensions that are particularly important to your application
- Assembly requirements or mating part considerations
- Packaging or shipping requirements
- Whether you need material certifications or test reports
- Any industry-specific requirements relevant to your application
- Budget constraints or target pricing
- Preferred communication methods
If you’re working under a purchase order system, need specific invoice formats, or have other administrative requirements, mention those as well. Addressing these details upfront prevents surprises later in the process.
How Complete RFQ Information Benefits Your Project
Providing complete information in your RFQ creates several advantages that benefit both you and the machine shop.
Improved Quoting Accuracy
When a machine shop has all the information needed to evaluate your project, the quote reflects the actual scope of work. Incomplete information forces the shop to make assumptions or provide quotes with qualifications and exclusions. A quote based on complete information is more likely to match the final invoice.
Reduced Back-and-Forth Questions
Every missing piece of information requires a follow-up question. This back-and-forth extends the time it takes to receive your quote and increases the chance of miscommunication. A complete RFQ allows the machine shop to provide a comprehensive quote in the first response.
Faster Turnaround
When your RFQ includes everything needed for quoting, the machine shop can prioritize it and provide a response quickly. Incomplete RFQs often sit in a queue waiting for clarification, delaying your entire project timeline.
Earlier Identification of Manufacturing Issues
A complete RFQ allows the machine shop to thoroughly review your design for manufacturability. Potential issues such as difficult-to-reach features, tolerance stack-ups, or material availability problems can be identified during quoting rather than after you’ve placed an order. This early feedback can save significant time and cost.
CNC Machining RFQ Checklist
Use this checklist when preparing your next CNC machining RFQ:
- Engineering drawing with all dimensions, tolerances, and notes
- CAD file in a compatible format (STEP preferred)
- Material specification with grade and condition
- Quantity needed and any future volume expectations
- General and specific tolerance requirements
- Surface finish requirements for all surfaces
- Required completion date or lead time
- Inspection and documentation requirements
- Secondary operations needed (finishing, heat treat, etc.)
- Special requirements or critical features
- Shipping address and preferred method
- Contact information for questions
Request a Quote from Anco Precision
At Anco Precision, we work with engineers, purchasing managers, and manufacturers who need reliable CNC machining for their projects. Whether you’re developing prototypes or need production quantities, we provide the precision machining and attention to detail your project requires.
When you’re ready to request a quote, use the information outlined in this article to prepare a complete RFQ. The more information you provide upfront, the more accurate and timely our quote will be. We’re also happy to discuss your project requirements and provide input on manufacturability and cost-effective approaches.
Contact Anco Precision today to request a quote for your CNC machining project. We’re located in Deerfield Beach, Florida, and we’re ready to help you move your project forward.