Precision Surface Finish Services

Precision Surface Finishing for Enhanced Performance & Durability

Precision surface finishing at Yueyi Precision goes far beyond visual appeal — it is a critical engineering factor that directly influences friction, wear resistance, corrosion protection, sealing performance, and component longevity. We provide advanced surface finishing solutions designed to meet both functional requirements and aesthetic expectations, ensuring your parts perform reliably in demanding industrial environments.

About Yueyi Precision

Surface Roughness Parameters & Measurement Standards

We measure and control surface texture using international standards to ensure consistent results across all manufacturing processes.

ACTIVE SPECIFICATION DETAIL

Arithmetic average of absolute values

Importance

Ra is the most widely used surface roughness parameter, typically specified for sealing surfaces, sliding interfaces, and general machined components.

Where Ra Surface Roughness Is Used

Ra surface roughness is commonly specified for functional surfaces where controlled friction, sealing performance, and wear resistance are critical. Typical applications include sealing faces, sliding components, bearing seats, and precision mating parts.

Ra Value (µm)	Surface Quality Description	Typical Manufacturing Process	Common Applications
12.5 µm	Very rough surface	Sand casting, flame cutting	Non-functional structural parts
6.3 µm	Rough machining finish	Rough turning, milling	Hidden or non-contact surfaces
3.2 µm	Standard machined finish	CNC milling, turning	General mechanical components
1.6 µm	Smooth machined surface	Fine machining, reaming	Bearing seats, sliding parts
0.8 µm	Fine surface finish	Grinding	Sealing surfaces, precision fits
0.4 µm	Very fine surface	Fine grinding, honing	Hydraulic components, valve parts
0.2 µm	Mirror-like surface	Polishing, lapping	Optical, medical, high-precision parts

ACTIVE SPECIFICATION DETAIL

Average maximum peak-to-valley height

Importance

Better for detecting irregularities

Where Rz Surface Roughness Is Used

Rz is often specified when peak-to-valley height matters—helpful for detecting irregularities that Ra may not fully capture. It’s commonly used for sealing surfaces, sliding interfaces, wear-critical parts, and finishes where maximum surface variation impacts performance.

Parameter	Definition	Typical Use	Notes
Rz	Average maximum peak-to-valley height measured over several sampling lengths. It represents the average height difference between the highest peak and lowest valley in each section.	Used where peak height and valley depth affect performance, such as sealing faces, sliding interfaces, and wear-critical surfaces.	Rz reflects extreme surface variation more clearly than average-based parameters.
Unit	µm (micrometers)	Engineering drawings & surface finish specifications	Always confirm the unit specified on the technical drawing.
What it measures	The vertical distance between the highest peak and lowest valley within each sampling length, averaged across multiple segments.	Functional surfaces where height variation influences sealing, friction, or contact behavior.	More sensitive to pronounced peaks and valleys than parameters based purely on averages.
When to specify Rz	When maximum surface variation is more important than overall smoothness.	Seal interfaces, hydraulic components, bearing seats, and precision contact surfaces.	Often specified together with other roughness parameters to fully define surface behavior.

ACTIVE SPECIFICATION DETAIL

Maximum peak-to-valley height

Importance

Critical for sealing surfaces

Where Rt Surface Roughness Is Used

Rt is specified when the total peak-to-valley height of a surface must be fully considered. It represents the maximum vertical distance within the evaluation length and is important for sealing faces, wear-critical interfaces, and applications where extreme surface variation can impact performance, contact behavior, or coating adhesion.

Parameter	Definition	Typical Use	Notes
Rt	Total height of the roughness profile from highest peak to deepest valley	Critical sealing surfaces, high-performance interfaces	Represents the full vertical range of surface texture
Unit	µm (micrometers)	Engineering drawings & surface finish specs	Always confirm the unit on the print
Common spec range	Depends on process (milling, turning, grinding, polishing)	Applications where maximum surface variation impacts performance	More extreme than Rz and Ra
When to choose Rt	When full surface peak-to-valley height must be controlled	Seal leakage control, wear-critical parts, coating adhesion	Most sensitive to isolated deep scratches or high peaks

ACTIVE SPECIFICATION DETAIL

Root mean square average

Importance

Statistical process control

Where Rq Surface Roughness Is Used

Rq (Root Mean Square Roughness) emphasizes larger surface deviations because it uses a square-averaging method. It is commonly used in statistical process control, precision machining analysis, and functional surfaces where variation consistency and surface energy behavior are important.

Parameter	Definition	Typical Use	Notes
Rq	Root Mean Square average of surface deviations	Precision parts, optical surfaces, statistical process control	More sensitive to peaks and valleys than Ra
Unit	µm (micrometers)	Engineering drawings & surface finish specifications	Always confirm the unit on the print
Common Spec Range	Depends on process (grinding, polishing, fine machining)	High-precision and functional surfaces	Used when consistency of surface variation matters
When to Choose Rq	When larger deviations must influence the result	Optical, sealing, and precision sliding components	Rq will always be equal to or higher than Ra

ACTIVE SPECIFICATION DETAIL

Single largest peak-to-valley

Importance

Worst-case scenario analysis

Where Rmax Surface Roughness Is Used

Rmax represents the single largest peak-to-valley height within the evaluation length. It is used for worst-case surface condition analysis, especially where one extreme surface defect could affect sealing, coating performance, or contact reliability.

Parameter	Definition	Typical Use	Notes
Rmax	The single largest peak-to-valley height measured within the evaluation length.	Worst-case control for sealing faces, sliding interfaces, and wear-critical surfaces.	More sensitive than Ra to one deep scratch or isolated burr. Often used with Ra/Rz.
Unit	µm (micrometers)	Engineering drawings & surface finish specifications	Always confirm unit on the drawing (µm is most common).
What it captures	Extreme surface defects (single deepest valley / highest peak).	Leak-risk surfaces, friction-sensitive contacts, critical fits	If Ra looks acceptable but sealing fails, Rmax often reveals the cause.
Common Spec Range	Process-dependent (turning/milling/grinding/polishing)	Functional surfaces requiring stable performance	Specify together with process/finish requirement to avoid ambiguity.
When to choose Rmax	When the “worst point” matters more than the average.	Gaskets, O-ring grooves, valve seats, hydraulic sealing surfaces	Use Rmax to limit outliers that Ra can “average out”.

About Yueyi Precision

Standard Machining Surface Finishes

> About Yueyi Precision

Arithmetic average of absolute values

Decorative, mild corrosion resistance

Thickness Range

5-25 μm

Surface Roughness Impact

Ra increases 0.1-0.3 μm

Color Options

Decorative, mild corrosion resistance

Surface Treatment & Coating Services

Type II Anodizing

Decorative, mild corrosion resistance

Thickness Range

5-25 μm

Surface Roughness Impact

Ra increases 0.1-0.3 μm

Color Options

Clear, black, gold, colors

Type III Hard Anodize

Wear resistance, electrical insulation

Thickness Range

25-100 μm

Surface Roughness Impact

Ra increases 0.3-1.0 μm

Color Options

Gray, black, dark green

Electroless Nickel

Uniform coverage, corrosion resistance

Thickness Range

5-50 μm

Surface Finish

Mirror to matte finish

Common Applications

Medical devices, food processing

Hard Chrome

Decorative, mild corrosion resistance

Thickness Range

10-250 μm

Surface Finish

Ra 0.1-0.8 μm

Common Applications

Hydraulic rods, mold surfaces

Powder Coating

Decorative, mild corrosion resistance

Dry Film Thickness

50-120 μm

Surface Preparation

Chemical pretreatment

Special Properties

Excellent chemical resistance, durable