Finish planning guidance
CNC Finishing Guide
Define the as-machined condition, required finish, cosmetic zones, masking, and finish-sensitive dimensions before requesting a CNC quote.
Short answer
A useful CNC finishing guide helps buyers define which surfaces stay as-machined, which move into anodizing, coating, polishing, blasting, or another post-process, and which dimensions or cosmetic zones must be accepted after finishing rather than before it.
Finishing is often treated as an afterthought even though it can change material choice, masking, edge expectations, inspection logic, and shipment acceptance. The stronger RFQ defines the finish path alongside the machined geometry so suppliers can quote one coherent requirement set. This page focuses on the information buyers should control before asking for a finishing-inclusive machining quote.
Applicability
CNC Finishing use cases
Machined parts with cosmetic, corrosion, wear, electrical, or cleanliness requirements that are not fully described by the as-machined condition alone.
Programs where the same geometry may be acceptable in different finish states depending on the end use or customer tier.
Quote reviews where masking, finish-sensitive dimensions, or show-surface standards need to be compared across suppliers.
RFQ inputs
RFQ inputs and drawing requirements
Base material and machined condition
State the approved substrate and the relevant as-machined requirement so finish reviewers know the condition they are starting from.
Exact finish specification
Call out the required finish type, color or appearance requirement when applicable, and any linked standard, note, or customer specification.
Cosmetic zones and masking
Mark visible surfaces, contact faces, threads, sealing features, or electrical keep-out zones that need special handling before finishing.
Final accepted condition
Identify which dimensions, textures, labels, or shipment records must be evaluated after finishing so the RFQ does not rely on pre-finish assumptions.
Constraints
Constraints and quote assumptions
- Finish requirements should be attached to the controlled drawing package and not added as vague late-stage notes after machining assumptions are already set.
- Cosmetic appearance and dimensional acceptance after finishing need separate definitions; one does not automatically describe the other.
- This guide does not claim blanket availability of every finish process or any unsupported certification, tolerance, or equipment detail; final routing depends on the submitted specification and part geometry.
Published standards
Where these terms are defined
These define the terms this page uses. ProtoRFQ claims no approval under any of them; the standard that governs a project is the one named in the RFQ.
- ISO 21920-2:2021 — the parameters a surface finish requirement is written in; a finish named only by process does not carry a measurable limit.
- ISO 7599:2018 — general specification method for decorative and protective anodic oxidation coatings on aluminium.
Related manufacturing examples
Related manufacturing references
Machined Mounting Plate
Machined Mounting Plate is a useful reference when flat machined surfaces later move into coating or anodizing and need clear show-surface rules.
Review reference
Machined Aluminum Frame
Machined Aluminum Frame shows why visible exterior surfaces should be separated from interior non-cosmetic areas before finishing is quoted.
Review reference
Machined Actuator Housing
Machined Actuator Housing helps frame finish-sensitive housings where pockets, bores, and exterior appearance all influence the accepted final condition.
Review referenceRelated pages
Continue the RFQ review
Surface finishes hub
Use the hub for finish-specific RFQ pages when the post-machining route has already been narrowed down.
Open pageAnodizing machined parts
Continue into one common finishing route when the part requirement specifically involves anodized aluminum.
Open pageCNC material selection guide
Review how base material decisions and finish plans interact before sending a quote package.
Open pageFAQ
CNC Finishing FAQs
Why should finish choices be decided before quoting?
Because finish requirements can affect material choice, masking, inspection, and packaging. Quoting them early reduces the risk of mismatched assumptions later in the job.
What finishing information is most often missing from RFQs?
The common gaps are no exact finish specification, no cosmetic-zone definition, and no statement of which dimensions or surfaces matter after the finish is applied.
Should a finishing RFQ distinguish as-machined and final condition?
Yes. Many finish-inclusive parts need both conditions understood, especially when coating growth, texture, or cosmetic acceptance is part of the decision.
Finish planning guidance
Quote machined parts from the full finishing requirement set.
Send the drawing, base material, finish specification, cosmetic-zone notes, and the dimensions that matter after finishing.
Start finishing RFQ