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Surface
roughness and finished
By definition,
surface finish is the allowable deviation from a perfectly flat
surface that is made by some manufacturing process. All machining
processes will produces some roughness on the surface. This roughness
can be caused by a cutting tool, cutting rate and environmental
conditions and the type of material you are working with.
Surface finish
is generally broken up into three components such as roughness,
waviness, and form.
Roughness
is generally the machined marks made on a surface by the cutting
tool.
Waviness is the result of the vibration of
the tool.
Form surface irregularities caused by worn
off machine bad, table etc.
All three surface
finish components exist simultaneously. They simply overlap one
another. We often look at each (roughness, waviness, and form) separately,
so we make the assumption that roughness has a shorter wavelength
than waviness, which in turn has a shorter wavelength than form.
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Ra = The
average variation from mean line.
Rt = Distance from the highest peak to the deepest valley.
Rz = The average Rt over a given length.
Rz=(Rp1+Rp2+Rp3)+(Rv1+Rv2+Rv3) / 3
Rp = The highest peak above the mean line.
Rv = The deepest valley below the mean line. |
|
| Surface
finish |
Ground,
Honed Roller, Burnished
|
Turned,
Boreed, Drilled
|
Rough
Machined
|
| N
Grade |
N1
|
N2
|
N3
|
N4
|
N5
|
N6
|
N7
|
N8
|
N9
|
N10
|
N11
|
N12
|
| Micro
Meter |
0.025
|
0.050
|
0.1
|
0.2
|
0.4
|
0.8
|
1,6
|
3,2
|
6.3
|
12,5
|
25
|
50
|
| Micro
Inch Ra |
1
|
2
|
4
|
8
|
16
|
32
|
63
|
125
|
250
|
500
|
1000
|
2000
|
| Rt |
8.7
|
17.4
|
34.8
|
69.6
|
139
|
278
|
548
|
1,088
|
2,175
|
4,350
|
8,700
|
17,400
|
| Rz |
7.0
|
14.0
|
28.0
|
56.0
|
112
|
224
|
441
|
875
|
1,750
|
3,500
|
7,000
|
14,000
|
| Rz
( ISO) |
7.6
|
15.2
|
30.4
|
60.8
|
122
|
243
|
479
|
950
|
1,900
|
3,800
|
7,600
|
15,200
|
| Ry
/ Rmax |
8.0
|
16.0
|
32.0
|
64.0
|
128
|
256
|
504
|
1,000
|
2,000
|
4,000
|
8,000
|
16,000
|
| Honing |
|
Honing
|
|
| Skive
and Roller Burnishing |
|
Skive
and Roller Burnishing
|
|
| Skiving
Only |
|
Skiving
Only
|
|
| Boring,
Drilling, Trepanning |
|
Boring,
Drilling, Trepanning
|
|
| Super
Finishing Grinding |
Super
Finishing Grinding
|
|
| Grinding |
|
Grinding
|
|
| Turning |
|
Turning
|
|
| Flame
Cutting |
|
Flame
Cutting
|
 
;
Surface
Texture and its symbol
|
|