Definition of surface roughness and expression reference

¡ô.Type of surface roughness:

Type

Average height of center line

Max. Height

Average height at Tpoint

Symbol

Ra

Rmax

Rz

Expression symbol
of maximum value
of maximum height

a

s

z

Definition

Absolute value area of roughness curve to center line is divided by datum length in ¦Ìm. Usually it can be directly read out via center line roughness measure.

Roughness curve

Center line

Measured length

Take a part of datum length from section curve, when the two straight lines parallel with this part of average line make this taken part narrow, measure the distance between two straight lines from curve's longitudinal magnification direction and express this value in ¦Ìm.

Longitudinal magnification direction

Average line

R Record
direction

Take a part of datum length from section curve, parallel with mean line but not to crosscut the section, so the difference from the line to the mean value between 5 peak elevations & 5 lowest elevations measured at curve's longitudinal magnification direction and express this value in ¦Ìm.

Datum length L

5 peak elevations
R2¡¢R3¡¢R6¡¢R8¡¢R10£º
Datum length L