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

5 Lowest elevations
Longitudinal magnification direction Average line
R Record
direction
 
  Symbol of
roughness		 Standard series Cutting value£¨mm£© Measured length£¨mm£© Standard series Datum length£¨mm£© Standard series Datum length£¨mm£©
Differentiation of standard symbol and datum length & roughness 0.013a 0.8 Cutting value£¾3 times 0.05s 0.25 0.05z 0.25
0.025a 0.1s 0.1z
0.05a 0.2s 0.2z
0.1a 0.4s 0.4z
0.2a 0.8s 0.8z
0.4a 1.6s 0.8 1.6z 0.8
0.8a 3.2s 3.2z
1.6a 6.3s 6.3z
3.2a 12.5s 2.5 12.5z 2.5
6.3a 25s 25z
12.5a 50s 8 50z 8
25a 2.5 100s 100z
- 50a 200s 25 200z 25
100a 400s 400z