Surface texture symbols

A surface-texture callout states the required finish for a surface. It may specify a roughness parameter such as Ra or Rz, a limit value, machining allowance or a required lay direction. Read the complete symbol and its notes together.

Roughness parameters

Ra describes average profile deviation over the defined evaluation length. Rz describes profile-height characteristics according to the specified standard. A value alone is incomplete unless the parameter and applicable measurement conditions are clear.

Manufacturing and inspection

A roughness requirement can affect machining method, tool condition, feed, material and inspection. Compare the drawing requirement with the actual manufacturing process and use a suitable measurement method.