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

1. Varieties of Surface Roughness Indicators 1. Positions of Auxiliary Symbols for Surface Symbol
Definitions and presentations of arithmetic average roughness(Ra), maximum height(Ry), 10 spot average roughness(Rz), average concave to A surface roughness value, cut-off value or reference length, machining method, grain direction, surface
convex distance(Sm), average distance between local peaks S and load length rate tp are given as parameters indicating the surface roughness of an undulation, etc. are indicated around the surface symbol as shown in Fig. 1 below.
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.] Fig. 1 Positions of Auxiliary Symbols
a : Ra Value
Typical calculations of surface roughness b : Machining Method
c : Cut-Off Value, Evaluation Length
Arithmetic Average Roughness Ra 1 R ◊ c' : Reference Length, Evaluation Length
Y Ra＝ R 0 f( ) dx
A portion stretching over a reference length in the direction in which the m d : Grain Direction
average line extends is cut out from the roughness curve. This portion f : Parameter other than Ra(tp:Parameter/Cut-Off Level)
is presented in a new graph with the X axis extending in the same Ra g : Surface Undulation(JIS B 0610)
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). Reference These symbols except a and f are provided when they are needed.
R Reference Under ISO 1302, a finish range should be indicated as e in Fig. 1.
Code Meaning Illustration
Maximum Height Ry R
A portion stretching over a reference length in the direction in which m The trace left by a cutting tool
the average line extends is cut out from the roughness curve. The gap is parallel to the projection
between the peak line and the trough line is measured in the direction Rp Ry plane in the drawing.
in which the magnitude axis extends, in microns(μm). Rv Ex. Shaped Surface Trace Left by a Cutting Tool
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
The trace left by a cutting
Ten-spot Average Roughness Rz m tool is perpendicular to the
1
A portion stretching over a reference length in the direction in Yp Yp2 3 Yp4 5 projection plane in the drawing.
which the average line extends is cut out from the roughness Yp Yp Ex. Shaped Surface(Side View)
curve. The average of the levels(Yp)of the highest peak to V1 Y YV2 YV3 YV4 V5 Y Circular Cut, Cylindrical Trace Left by a Cutting Tool
the fifth highest peak as measured from the average line R Cut
and the average of the levels(Yp)of the lowest trough to the Yp 1 ＋Yp 2＋Yp 3＋Yp ＋Yp 5 ＋ Yv1＋Yv ＋Yv ＋Yv 4 ＋Yv 5
2
4
3
fifth lowest trough similarly measured in the said portion are Rz＝ 5 The pattern left by a cutting tool
diagonally crosses the projection
added together. Rz is this sum, in microns(μm).
Yp1、Yp2、Yp3、Yp4、Yp5 ： Levels of the highest peak to the fifth highest peak plane in the drawing.
in the said portion with the reference length ℓ. Ex. Honed Surface
Levels of the lowest trough to the fifth lowest trough Trace Left by a Cutting Tool
Yv1、Yv2、Yv3、Yv4、Yv5 ：
in the said portion with the reference length ℓ.
The pattern left by a cutting tool
Reference Relation between Arithmetic Average Roughness(Ra)and Conventional Parameters crosses in various directions or
Arithmetic Average Roughness Maximum Height Ten-spot Average Reference Length of has no grain direction.
Ra Ry Roughness Rz RyCRz Conventional
Standard Series Cut-off Value c(mm) Graphical Representation of Surface Texture Standard Series R(mm) Finish Symbol Ex. Lapped Surface, Superfinished
Surface and Surface Finished
0.012a 0.08 0.05s 0.05z 0.08 with a Front Mill or End Mill
0.025a 0.25 0.1 s 0.1 z
0.05 a 0.012 ～ 0.2 0.2 s 0.2 z 0.25 The pattern left by a cutting
0.1 a 0.4 s 0.4 z tool is virtually concentric
0.2 a 0.8 s 0.8 z around the center of the plane
0.4 a 0.8 1.6 s 1.6 z in the drawing.
0.8 a 0.4 ～ 1.6 3.2 s 3.2 z 0.8 Ex. Faced Surface
1.6 a 6.3 s 6.3 z
3.2 a 2.5 3.2 ～ 6.3 12.5 s 12.5 z
6.3 a 25 s 25 z 2.5 The pattern left by a cutting
12.5 a 12.5 ～ 25 50 s 50 z tool is virtually radial around
25 a 8 100 s 100 z 8 the center of the plane in the
50 a 50 ～ 100 200 s 200 z drawing.
100 a － 400 s 400 z － ～
GInterrelations among the three types shown here are not precise, and are presented for convenience only.
GRa:The evaluation values of Ry and Rz are the cut-off value and the reference length each multiplied by five, respectively.
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