A physical part can tell a machine shop a great deal about its shape, but it does not always reveal the original design intent. Wear, repairs, missing features and unknown materials can make a sample misleading. If you need a replacement or a modified component, the way you prepare a part for reverse engineering can help clarify what must be reproduced and what may need to change.
From a CNC machine shop’s viewpoint, a useful sample is clean enough to examine, clearly identified and accompanied by information about how it fits and functions. The following checklist will help you organize that information before discussing the project or requesting a quote.
Start by defining the goal
Explain why you need the part and what a successful replacement must do. Are you replacing a worn component, documenting an existing design or changing a feature to solve a recurring problem? An exact copy of the sample is not always the right target: a worn bearing surface, for example, may no longer represent the size needed for a proper fit.
Identify the part’s intended function, operating environment and known failure mode. Note whether the replacement must fit an existing assembly and whether any dimensions are negotiable. Also confirm that you have the authority to reproduce the part and share any associated files.
Clean the part without removing evidence
Remove loose dirt, oil and debris so that important surfaces and features can be seen. Use a cleaning method appropriate to the material and any coatings, seals or bonded components. If you are unsure what the part is made of, avoid aggressive chemicals, abrasives or heat.
Do not sand, grind, straighten or repair the sample simply to make it look better. Those actions can change dimensions or hide evidence of how the part failed. If residue, corrosion or a coating may affect the analysis, photograph it before cleaning and explain what you removed. Ask the recipient about handling requirements before sending a part contaminated with hazardous material.
Keep small components together
Retain removable pins, fasteners, spacers and other pieces when they help explain the assembly. Place loose items in separate labeled bags rather than allowing them to scratch the sample. If disassembly is necessary, photograph the assembly first and record each item’s location and orientation. Do not force apart components that may be damaged in the process.
Label the sample and document its condition
Give each sample a unique identifier that matches your photos and project notes. Include a part number or revision if known, and identify which sample is the best representation of the intended design. Use a tag or packaging label rather than marking a functional surface.
Photograph the part from several angles in good lighting, including close-ups of important features. A scale in the image can provide context, although a photograph is not a substitute for a dimensioned drawing. Mark up copies of the photos to identify areas that deserve attention.
Describe damage and uncertainty explicitly. For example, indicate whether a chipped edge should be restored, a bent tab should be straight in the replacement, or a repaired weld is part of the desired design. Useful observations include:
- Wear tracks, scoring, cracks, corrosion or deformation.
- Missing pieces, broken threads or altered holes.
- Previous repairs, coatings or modifications.
- Features that are intact and should remain unchanged.
- Differences between multiple samples of the same part.
If a feature is damaged, provide another example, an older drawing or information about the mating part when available. Without that context, the original geometry may be uncertain; do not assume that a damaged sample can answer every design question.
Identify mating and functional features
A shop can observe the sample’s geometry, but the customer often knows which features control fit or performance. Point out surfaces that locate the part, holes used for alignment, threads, sealing areas, bearing seats and interfaces with adjacent components. Explain which face or edge establishes the part’s position in the assembly.
When practical, provide information about the mating components, such as their drawings, known dimensions or photos. Sending a mating component may also be useful, but coordinate that in advance. State whether a feature needs clearance, a close fit or a particular alignment, and provide the actual requirement if it is known. A note such as “must fit the existing shaft” is helpful context, but the shaft size and desired fit make the requirement more actionable.
Distinguish critical surfaces from cosmetic or nonfunctional ones. Tighter requirements can affect machining methods, inspection time and cost, so reserve them for features where they support the part’s function. If you do not know the necessary tolerances, say so and identify the features whose fit you are concerned about.
Collect existing specifications and files
Search for any documentation that can establish the intended design. Even an older drawing, a partial model or handwritten maintenance notes can provide useful context. Clearly identify which information is current and which may be outdated.
Drawings and CAD files
Send the latest engineering drawing and CAD files when available, including a STEP file if you have one. A three-dimensional model is useful for communicating geometry, while the drawing typically serves as the controlling specification. It can define dimensions, tolerances, finish and notes that may not be evident in the model. Identify any conflicts between the drawing, model and physical sample rather than leaving the shop to guess which one takes priority.
Material, finish and other requirements
State the material grade and condition if known. A sample’s appearance alone is not a reliable way to identify an alloy or material specification. If the material is unknown, say what you know about its use and whether an alternative is acceptable. Clarify whether a coating, heat treatment or surface finish is required, and identify which surfaces it applies to.
Include any customer-specified inspection requirements, reports, standards or certifications needed for the project. These are requirements to discuss during quoting, not assumptions about what a particular shop can provide. If acceptance depends on a test or a particular method of checking a feature, describe that as well.
Prepare the sample for shipment or handoff
Before sending anything, confirm that the recipient can review the physical part and agree on the handoff method. Protect functional surfaces from contact with other items, secure loose components separately and use packaging that keeps the sample from moving. Include a packing list with sample identifiers and contact information.
Say whether the sample must be returned and whether it can be disassembled or otherwise altered. If it is the only usable component or is needed to keep equipment running, make that limitation clear. Also communicate any handling concerns, including sharp edges, stored energy or residual process materials.
Prototype and production quantities affect the discussion
For a prototype or initial replacement, the main question may be whether the part fits and functions as intended. Tell the shop if you expect to test the first part, revise the design or approve a sample before ordering more. That plan can influence how the project is quoted and how open questions are resolved.
For production quantities, share both the immediate order quantity and any expected repeat demand, while distinguishing a forecast from a commitment. Consistent documentation, clearly defined acceptance criteria and a stable revision become especially important when parts must be reproduced over time. Quantity can also affect the economics of setup, material purchasing and machining choices.
Practical RFQ checklist
Before requesting a machining quote, gather the following information. If something is unknown, identify it as an open question rather than supplying a guess.
- Part identification: Part name, number, revision, sample identifiers and a brief description of its function.
- Engineering drawings: The current drawing, older references if relevant, and notes identifying any discrepancies.
- CAD files: Available models, including a STEP file when possible, with the applicable revision identified.
- Material: Grade and condition, or a clear statement that the material is unknown; note whether substitutes are acceptable.
- Quantity: The number needed now and any anticipated repeat requirements.
- Tolerances and critical features: Required dimensions, fits and datums where known, plus mating features and areas that must not be copied as worn.
- Surface finish: Finish, coating or treatment requirements and the surfaces they apply to.
- Required completion date: The needed delivery date and any intermediate approval or test schedule.
- Inspection requirements: Features to be checked, required documentation and any customer-specified standards or certifications.
- Special notes: Damage, prior repairs, sample handling and return instructions, open design questions and restrictions on acceptable changes.
Request a machining quote
If you have an active project, send Anco Precision your files and project requirements for review and request a machining quote. Include a drawing or STEP file when available, the material, quantity, tolerances or other critical requirements, and your required delivery date. If you have only a physical sample, describe its condition and mating features, and ask how best to share it before shipping.
Ready to Request a CNC Machining Quote?
If you have an active machining project, send Anco Precision your drawing or STEP/CAD file when available, along with the material, quantity, critical requirements, and desired delivery date. Request a CNC machining quote so the project can be reviewed for pricing.