As-Machined
Standard CNC machined surface finish with visible tool marks. The most cost-effective option with typical surface roughness of Ra 1.6-3.2 µm. Ideal for non-cosmetic and internal parts.
About As-Machined
As-machined is the standard surface finish produced directly by the CNC milling or turning process with no additional finishing operations. The surface exhibits visible tool marks, feed lines, and step-over patterns that are characteristic of the toolpath strategy used during machining. With typical surface roughness of Ra 1.6-3.2 µm, it is the fastest and most economical surface finish option available, as it requires no secondary processing, additional time, or added cost.
As-machined finish is the default and most commonly specified option for functional, non-cosmetic parts such as internal mechanisms, structural brackets, jigs, fixtures, prototype iterations, and engineering test parts. It is included at no additional charge with all CNC machining orders and provides excellent dimensional accuracy and repeatability. The visible tool marks do not affect the mechanical performance of the part in the vast majority of applications.
While the as-machined surface is not suitable for high-visibility consumer products or optical applications, it is perfectly adequate for the majority of industrial, prototyping, and engineering applications. Parts can always be post-processed with bead blasting, polishing, anodizing, or coating later if cosmetic requirements change. For prototyping workflows, as-machined finish enables the fastest possible turnaround time by eliminating all secondary processing steps from the production schedule.
Finish Properties
How It Works
The as-machined surface finish is the natural result of the CNC milling or turning process. During milling, the rotating cutting tool traces overlapping passes across the surface, leaving a pattern of feed marks (parallel lines from the tool feed direction) and step-over marks (scallops from adjacent toolpath passes). During turning, the single-point tool leaves a helical feed mark pattern as the workpiece rotates. The surface roughness is determined by the feed rate, step-over distance, tool nose radius, spindle speed, and material properties. Standard machining parameters are optimized for a balance of material removal rate, tool life, and surface quality, resulting in Ra 1.6-3.2 µm without any specialized finish passes.
Design Guidelines for As-Machined
Specify as-machined for all non-cosmetic surfaces and internal features to minimize cost and lead time—only call out smoother finishes where functionally required.
Be aware that sharp internal corners will show tool radius marks—if cosmetic appearance matters, add fillets or specify these surfaces for additional finishing.
Deburring is included with as-machined finish—sharp edges and burrs from machining are removed, but the surface texture itself is not altered.
If you plan to add coatings later (anodizing, powder coating), the as-machined surface provides adequate adhesion for most coatings without additional preparation, though bead blasting beforehand will improve coating uniformity.
Document acceptance criteria for as-machined surfaces (e.g., "tool marks acceptable, no burrs, no scratches") in your drawing notes to avoid subjective quality disputes.
Compatible Materials
Materials that can be finished with as-machined.
As-Machined FAQ
An as-machined surface has a consistent metallic appearance with visible parallel feed lines from the cutting tool. Milled surfaces show a cross-hatched or linear pattern depending on the toolpath strategy. Turned surfaces show fine concentric or helical lines. The surface has a slight matte sheen and is smooth to the touch but not glossy. Tool marks are visible under normal lighting conditions and can be felt with a fingernail drawn across the surface.
Surface quality varies somewhat by material. Aluminum and brass typically produce the smoothest as-machined surfaces (Ra 1.2-2.0 µm) due to their excellent machinability. Stainless steel and titanium tend to produce slightly rougher surfaces (Ra 2.0-3.2 µm) due to work hardening and built-up edge formation. Plastics vary widely—POM produces very smooth surfaces while glass-filled nylon may show fiber pullout and a rougher texture.
Yes, this is standard practice and recommended. Use surface finish symbols on your technical drawing to call out specific Ra requirements on critical surfaces (e.g., sealing faces at Ra 0.8 µm) while leaving non-critical surfaces at the default as-machined finish. This approach optimizes cost by concentrating finish machining effort only where it is needed.
Yes. All FabRapid CNC machined parts include manual deburring of sharp edges and removal of machining burrs as standard practice, regardless of the specified surface finish. This ensures safe handling and proper fit of assembled components. Edge break is typically 0.1-0.3 mm unless a specific chamfer or radius is specified in the drawing.
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