Mechanical Engineering Drawing Workshop

Reference of Surface TextureRa(μm)Function

Finishing

0.05

mirror surface

lapping

0.1

emery paper

0.2 0.4surface for sliding O-ring

fine machining

0.8surface for O-ring flange

electrical discharge machining

1.6 3.2～6.3^10

fits

normal machining

12.5～25^50

Table 8: Standard numbers of “Ra”.