Page 1656 - MiSUMi 2025

[Technical Data]
Surface Roughness
JIS B 0601 (1994)
Excerpts from JIS B 0031 (1994)

1. Varieties of Surface Roughness Indicators
Definitions and presentations of arithmetic average roughness (Ra), maximum height (Ry), 10 spot average
roughness (Rz), average concave to convex distance (Sm), average distance between local peaks S and
load length rate tp are given as parameters indicating the surface roughness of an industrial product. Surface
roughness is the arithmetical average of values at randomly extracted spots on the surface of an object.
[Centerline average roughness (Ra75) is defined in the supplements to JIS B 0031·JIS B 0601.]

Typical calculations of surface roughness
Arithmetic Average Roughness Ra 1 R ◊
Y Ra＝ R 0 f( ) dx
A portion stretching over a reference length in the direction in which the m
average line extends is cut out from the roughness curve. This portion
is presented in a new graph with the X axis extending in the same Ra
direction as the average line and the Y axis representing the magnitude. 0 X
Ra is represented by the equation shown at right, in microns (μm).
R
Maximum Height Ry R
A portion stretching over a reference length in the direction in which m
the average line extends is cut out from the roughness curve. The gap
between the peak line and the trough line is measured in the direction Rp Ry
in which the magnitude axis extends, in microns (μm). Rv
Reference A Portion without an abnormally high peak or abnormally low trough,
which may be regarded as a flaw, is cut out over the reference length. Ry＝Rp＋Rv
Ten-spot Average Roughness Rz m
A portion stretching over a reference length in the direction in 1 Yp Yp2 3 Yp4 5
which the average line extends is cut out from the roughness Yp Yp
curve. The average of the levels (Yp) of the highest peak V1 Y YV2 YV3 YV4 V5 Y
to the fifth highest peak as measured from the average line R
and the average of the levels (Yp) of the lowest trough to the Yp 1 ＋Yp 2＋Yp 3＋Yp ＋Yp Yv1＋Yv ＋Yv ＋Yv 4 ＋Yv 5
4
2
3
fifth lowest trough similarly measured in the said portion are Rz＝ 5 ＋
5
added together. Rz is this sum, in microns (μm).
Yp1、Yp2、Yp3、Yp4、Yp5 ： Levels of the highest peak to the fifth highest peak
in the said portion with the reference length ℓ.
Levels of the lowest trough to the fifth lowest trough
Yv1、Yv2、Yv3、Yv4、Yv5 ：
in the said portion with the reference length ℓ.
Reference Relation between Arithmetic Average Roughness (Ra) and Conventional Parameters
Arithmetic Average Roughness Maximum Height Ten-spot Average Reference Length of
Ra Ry Roughness Rz RyCRz Conventional
Standard Series Cut-off Value c (mm) Graphical Representation of Surface Texture Standard Series R(mm) Finish Symbol
0.012a 0.08 0.05s 0.05z
0.025a 0.25 0.1s 0.1z 0.08
0.05a 0.012 ～ 0.2 0.2s 0.2z 0.25
0.1a 0.4s 0.4z
0.2a 0.8s 0.8z
0.4a 0.8 1.6s 1.6z 0.8
0.8a 0.4 ～ 1.6 3.2s 3.2z
1.6a 6.3s 6.3z
3.2a 2.5 3.2 ～ 6.3 12.5s 12.5z
6.3a 25s 25z 2.5
12.5a 12.5 ～ 25 50s 50z
25a 8 100s 100z 8
50a 50 ～ 100 200s 200z
100a － 400s 400z － ～
GInterrelations among the three types shown here are not precise, and are presented for convenience only.
GRa: Ry, Rz - The evaluation length is obtained by multiplying the cut-off value and the standard value by 5 respectively.
B-011