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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

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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 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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2. METHODS OF MEASURING S. FINISH

1. SURFACE INSPECTION BY COMPARISON

MEHODS: these include:

i. Touch inspection

ii. Visual inspection

iii. Scratch inspection

iv. Microscopic inspectioon

v. Surface photographs

vi. Micro interferromter

vii. Wallace surface dynamometer

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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, while24/03/2012 6Lec # 27 & 28


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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. 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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