Surface roughness can be defined as the deviation of a surface’s normal away from the normal of an ideally flat surface. Surface roughness is a critical factor for machined parts and finished goods because of its effect on their mechanical properties, performance out in the field, and failure susceptibility. A high surface roughness can be detrimental because it can increase a part’s tendency to corrode faster and wear faster from friction. But, high surface roughness can also be beneficial by promoting a strong bond between a part and an adhesive. Ebatco’s NAT lab has acquired a Surftest SJ-210 Portable Surface Roughness Tester, manufactured by Mitutoyo, which can perform surface roughness analysis on samples of varying sizes. The SJ-210 instrument uses a contact stylus to make physical contact with the sample surface. The diamond stylus tip is dragged across the sample surface while remaining in contact under a specified contact force. The vertical displacement of the stylus tip is recorded as a function of horizontal distance traveled. This displacement data is used to produce a line profile from which over 40 different roughness parameters can be calculated: such as average roughness and root mean square roughness, along with bearing area and amplitude distribution curves. By modifying the sampling length (λs), cut off length (λc), and evaluation length used in the measurement, the Surftest SJ-210 can analyze samples in accordance with different ISO, and ANSI standards.

Typical Experimental Results

Surface roughness line profile of a diamond like carbon (DLC) coating on a steel substrate.
Surface roughness line profile of the Surftest’s precision roughness standard.

Applications

AdhesivesCeramicsCoatingsContact Mechanics
Failure AnalysisForeign Material
Identification		Forensic
Analysis		Fractography
FrictionLubricationMaterialsMetals
PolymersSurface AnalysisTribologyWear

Instrument: Surftest SJ-210 Portable Surface Roughness Tester

Key Specifications

X Axis Measurement Range Up to 17.5 mm
Z Axis Measurement Range 360 µm
Z Axis Measurement Resolution 0.02 µm – 0.002 µm
Measurement Accuracy ± 2%
Sampling Length (λs)/Cut Off Length (λc) Range 0.08 mm – 2.50 mm
Contact Force 0.75 mN
Stylus Tip Material Diamond
Stylus Tip Geometry 60°, 2 µm tip radius or curvature
Assessed Profiles Primary Profile, Roughness Profile, DF Profile, Roughness Profile-Motif

 

ASTM Number Title Website Link
D2663 – 14 Standard Test Methods for
Carbon Black—Dispersion in Rubber		 Link
D7127 – 17 Standard Test Method for Measurement
of Surface Roughness of Abrasive Blast
Cleaned Metal Surfaces Using a
Portable Stylus Instrument		 Link
E384 – 17 Standard Test Method for
Microindentation Hardness of
Materials		 Link
F1811-97(2002) Standard Practice for Estimating the
Power Spectral Density Function and
Related Finish Parameters from
Surface Profile Data		 Link
F2215 – 15 Standard Specification for Balls,
Bearings, Ferrous and Nonferrous for
Use in Bearings, Valves, and
Bearing Applications		 Link
ISO Number Title Website Link
10110-8:2010 Optics and photonics — Preparation
of drawings for optical elements and
systems — Part 8: Surface texture;
roughness and waviness		 Link
12129-2:1995 Plain bearings — Part 2: Tolerances
on form and position and surface
roughness for shafts, flanges and
thrust collars		 Link
19606:2017 Fine ceramics (advanced ceramics,
advanced technical ceramics) — Test
method for surface roughness of fine
ceramic films by atomic force microscopy		 Link
2037:1992 Stainless steel tubes for the food industry Link
23519:2010 Sintered metal materials, excluding
hardmetals — Measurement of surface
roughness		 Link
4287:1997 Geometrical Product Specifications
(GPS) — Surface texture: Profile method —
Terms, definitions and surface texture
parameters		 Link
8503-5:2017 Preparation of steel substrates before
application of paints and related
products — Surface roughness
characteristics
of blast-cleaned steel substrates — Part 5:
Replica tape method for the
determination
of the surface profile		 Link