1. MEASUREMENT OF SURFACE FINISH
SURFACE TEXTURE:
“ The characteristics quality of an actual surface due to small departures from its general geometrical form which, occurring at regular or irregular intervals, tend to form a pattern or texture on the surface”
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2. 1. SURFACE TEXTURE
“The General form” relates to the dominant shape of surface which it is intended to reproduce, & constitute a first approximation to the design form
It is possible for two or more kind of irregularity to be combined in the complete texture of a surface in such a way that they are not readily distinguishable individually by eye or touch
Surface texture varies according to the machining processes used in producing it (eg. Metal machining)
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3. 1. SURFACE TEXTURE
Difference in surface texture are apparent by visual examination & can be felt readily by passing a finger nail over the surface
The texture of surfaces can be regular or non-regular in character
FACTORS PRODUCING SURFACE IRREGULARITY:
Faulty tools
Inherent imperfections in the m/c tools
Errors due to personal element
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4. 2. METHODS OF MEASURING S. FINISH
SURFACE INSPECTION BY COMPARISON MEHODS: these include:
Touch inspection
Visual inspection
Scratch inspection
Microscopic inspectioon
Surface photographs
Micro interferromter
Wallace surface dynamometer
Reflected light intensity
Comparison by standard specimens
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5. 2. METHODS OF MEASURING S. FINISH
Direct Instrument Measurement
Intersection method
Interference method
Stylus method
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6. 3. NUMERICAL EVALUATION OF SURFACE TEXTURE
Practice adopted for obtaining numerical evaluation of surface texture is to use a parameter based on the cross-sectional profile of the surface under examination
There are two system for Numerical evaluation of surface finish, i.e:
Centre line average (CLA)
Root mean square (RMS) value of height undulations of the surface
The CLA system is more popular in UK, while the RMS is more popular in USA
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7. 3. NUMERICAL EVALUATION OF SURFACE TEXTURE
FOR EQUATIONS of CLA & RMS,
AS DEOMOSNTRATED ON BOARD
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8. 4. TOMLINSON SURFACE FINISH RECORDER
As Demonstrated for figure on next slide on board
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9. 4. TOMLINSON SURFACE FINISH RECORDER
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10. 5. ADVERSE EFFECTS OF POOR SURFACE FINISH
Book: Engineering metrology & instrumentation Page#: 234 DO YOUR SELF
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