Surface Texture Symbols

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Surface Texture Symbols

• CHAPTER 12
• INSTRUCTOR M.YAQUB

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12.22 Surface Roughness, Waviness, and Lay

• The modern demands of the automobile, the
  airplane, and other modern machines (heavier
  loads, higher speeds with less friction) need for
  accurate control of surface.
• The system of surface texture symbols recommended
  by ANSI/ASME.

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Surface Texture Symbols

• Not all surfaces can be finished because of cost
  constrains. Few surfaces requires special surface
  finish and should indicate on drawing by using
  surface finish symbol.

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DefinationsRoughness CLA or Roughness height
(Ra)Average of roughness height over a certain
length Roughness-width Cut off The length over
which roughness is average Roughness
Width Horizontal distance between two similar
point
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Waviness Width Overall widthWaviness
Height Overall height Lay Direction Mark of
machining on surfaceFlaw Defect on material
surface
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Surface texture symbol
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Additional Information

• Usually all information are not required. Only
  roughness height and machine allowance is
  important. In this case basic symbol is used.
• Roughness height in mm or in m inch. All other in
  mm or inch.

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Example
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