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MEASUREMENT OF SURFACE FINISH

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”. 1. SURFACE TEXTURE.

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MEASUREMENT OF SURFACE FINISH

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  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” Lec # 27 & 28

  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) Lec # 27 & 28

  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 Lec # 27 & 28

  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 Lec # 27 & 28

  5. 2. METHODS OF MEASURING S. FINISH • Direct Instrument Measurement • Intersection method • Interference method • Stylus method Lec # 27 & 28

  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 Lec # 27 & 28

  7. 3. NUMERICAL EVALUATION OF SURFACE TEXTURE FOR EQUATIONS of CLA & RMS, AS DEOMOSNTRATED ON BOARD Lec # 27 & 28

  8. 4. TOMLINSON SURFACE FINISH RECORDER As Demonstrated for figure on next slide on board Lec # 27 & 28

  9. 4. TOMLINSON SURFACE FINISH RECORDER Lec # 27 & 28

  10. 5. ADVERSE EFFECTS OF POOR SURFACE FINISH Book: Engineering metrology & instrumentation Page#: 234 DO YOUR SELF Lec # 27 & 28

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