MEASUREMENT OF SURFACE FINISH
1. 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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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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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 nonregular in character
– FACTORS PRODUCING SURFACE IRREGULARITY:
• Faulty tools
• Inherent imperfections in the m/c tools
• Errors due to personal element
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2. METHODS OF MEASURING S. FINISH
1. SURFACE INSPECTION BY COMPARISON
MEHODS: these include:
i.
ii.
iii.
iv.
v.
vi.
vii.
viii.
ix.
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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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2. METHODS OF MEASURING S. FINISH
2. Direct Instrument Measurement
i. Intersection method
ii. Interference method
iii. Stylus method
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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:
a. Centre line average (CLA)
b. 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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3. NUMERICAL EVALUATION OF SURFACE
TEXTURE
FOR EQUATIONS of CLA & RMS,
AS DEOMOSNTRATED ON BOARD
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4.
TOMLINSON SURFACE FINISH
RECORDER
As Demonstrated for figure on next slide on
board
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4.
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TOMLINSON SURFACE FINISH
RECORDER
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5.
ADVERSE EFFECTS OF POOR
SURFACE FINISH
Book: Engineering metrology & instrumentation
Page#: 234
DO YOUR SELF
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