Surface Texture Symbols

CHAPTER 12

INSTRUCTOR: M.YAQUB

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.

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.

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

Waviness Width: Overall widthWaviness Height: Overall height Lay Direction: Mark of machining on surface

Flaw: Defect on material surface

Surface texture symbol

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 m or in inch. All other in mm or inch.

Example