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Surface Finish Degree (Smoothness)
Comparison Table
between Rz, Ra and RMS for Iron and Steel Castings
What standard can be used for the surface finish
degree, or we called smoothness degree for the iron
and steel castings?
The following comparison table was
organized by us. You can find the comparison
for the new standard in China for the Ra and Rz, and
the micron, microinch Ra in USA. In addtion,
we also lised the old grades in China for your
reference. The old grades are still widely used in
China. We usually called the
Downward-pointing Triangle as "hwar". However, we do
not suggest the purchasers or buyers to denoted the
China old grades on the drawings or inquirements.
The comparison is just for your reference, should
not be taken as the inspection standard.
This article is from
www.iron-foundry.com Please keep this link!
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BLOG.
|
China Old Grade |
China New
Ra |
China New
Rz |
USA micron
Ra |
USA microinch
Ra |
|
▽
1 |
50 |
200 |
|
|
|
▽
2 |
25 |
100 |
|
|
|
▽
3 |
12.5 |
50 |
|
|
|
▽
4 |
6.3 |
25 |
8.00 |
320 |
|
6.30 |
250 |
|
▽
5 |
3.2 |
12.5 |
5.00 |
200 |
|
4.00 |
160 |
|
3.20 |
125 |
|
▽
6 |
1.6 |
6.3 |
2.50 |
100 |
|
2.00 |
80 |
|
1.60 |
63 |
|
▽
7 |
0.8 |
6.3 |
1.25 |
50 |
|
1.00 |
40 |
|
0.80 |
32 |
|
▽
8 |
0.4 |
3.2 |
0.63 |
25 |
|
0.50 |
20 |
|
0.40 |
16 |
|
▽
9 |
0.2 |
1.6 |
0.20 |
12.5 |
|
10 |
|
8 |
|
▽
10 |
0.1 |
0.8 |
0.10 |
|
|
RMS (microinch) |
RMS
(µm) |
RA (microinch) |
RA
(µm) |
Grit Size |
|
80 58
47
34
17
14 |
2.03 1.47
1.2
0.6
0.43
0.36 |
71 52
42
30
15
12 |
1.90 1.32
1.06
0.76
0.38
0.30 |
80 120
150
180
240
320 |
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