Surface Finish (Cf) and Manufacturing Processes
The chart below shows the surface roughness capablity of various manufacturing processes.
Variations on this chart can be found almost anywhere. We think it originated in
Machinery's Handbook!
Surface Roughness Chart - Shows the roughness average for different manufacturing processes in micrometers and micro-inches.
The values are shown with a typical range and a less frequent range for each manufacturing process.
As a general rule the lower on the chart and further to the right means a more costly process.
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Manufacturing Process |
Roughness Average (Ra)
Micrometers (Micro-inches) |
Forming Processes |
50 (2000) |
25 (1000) |
12.5 (500) |
6.3 (250) |
3.2 (125) |
1.6 (63) |
0.80 (32) |
0.40 (16) |
0.20 (8) |
0.10 (4) |
0.05 (2) |
0.025 (1) |
0.012 (.5) |
Sand Casting |
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Hot Rolling |
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Forging |
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Permanent Mold Casting |
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Investment Casting |
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Extruding |
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Cold Rolling, Drawing |
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Die Casting |
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Metal removal or cutting processes |
50 (2000) |
25 (1000) |
12.5 (500) |
6.3 (250) |
3.2 (125) |
1.6 (63) |
0.80 (32) |
0.40 (16) |
0.20 (8) |
0.10 (4) |
0.05 (2) |
0.025 (1) |
0.012 (.5) |
Flame Cutting |
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Snagging |
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Sawing |
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Planing, Shaping |
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Drilling |
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Chemical Milling |
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Elect Discharge Machining |
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Milling |
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Broaching |
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Reaming |
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Electron Beam |
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Laser |
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Electro-Chemical |
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Boring, Turning |
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Finishing processes |
50 (2000) |
25 (1000) |
12.5 (500) |
6.3 (250) |
3.2 (125) |
1.6 (63) |
0.80 (32) |
0.40 (16) |
0.20 (8) |
0.10 (4) |
0.05 (2) |
0.025 (1) |
0.012 (.5) |
Barrel Finishing |
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Electrolytic Grinding |
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Roller Burnishing |
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Grinding |
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Honing |
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Electro-Polish |
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Polishing |
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Lapping |
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Super Finishing |
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50 (2000) |
25 (1000) |
12.5 (500) |
6.3 (250) |
3.2 (125) |
1.6 (63) |
0.80 (32) |
0.40 (16) |
0.20 (8) |
0.10 (4) |
0.05 (2) |
0.025 (1) |
0.012 (.5) |
Surface Finish (Cf) and Tolerance (Ct) Impact on Component Cost
Basically the finer the finish and the tigher the tolerance the greater the cost.
Ideally from a cost impact point of view it is best for the designer to accept the
finish and tolerance capability of the primary process.
Part performance and functioning
usually dictates that this is not possible so consideration must be given to what
kind of secondary processes will be required to enable the component to perform as
desired.
The subject is discussed at length in Chapter Six of the book "Process and Operation
Planning: Revised Edition of the Principles of Process Planning, A Logical Approach"
-
by G. Halevi - See Below