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.

      Average Range       Less Frequent Range

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                                                    
Hot Rolling                                                    
Forging                                                    
Permanent Mold Casting                                                    
Investment Casting                                                    
Extruding                                                    
Cold Rolling, Drawing                                                    
Die Casting                                                    
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                                                    
Snagging                                                    
Sawing                                                    
Planing, Shaping                                                    
Drilling                                                    
Chemical Milling                                                    
Elect Discharge Machining                                                    
Milling                                                    
Broaching                                                    
Reaming                                                    
Electron Beam                                                    
Laser                                                    
Electro-Chemical                                                    
Boring, Turning                                                    
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                                                    
Electrolytic Grinding                                                    
Roller Burnishing                                                    
Grinding                                                    
Honing                                                    
Electro-Polish                                                    
Polishing                                                    
Lapping                                                    
Super Finishing                                                    
  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  

The charts below show the relationship between Tolerance and Surface Roughness.

Finish tolerance and process costs for cost estimating

Surface Roughness
Ra (um)
25.0012.509.126.255.003.752.502.121.801.601.321.000.800.450.32>0.20
Tolerance
+/- (mm)
1.000.600.350.250.200.150.100.080.060.050.040.030.020.020.01<0.005

Title


Author : Publisher
ISBN

Cover

Remarks

Relevant books are listed below. Click on the cover image and you will be taken to the Amazon bookstore.
Process and Operation Planning: Revised Edition of the Principles of Process Planning, A Logical Approach
G. Halevi : Kluwer Academic
ISBN: 1-4020-1653-0
Target Costing Shows that process planning, now fully integrated in the manufacturing system, can be regarded as a science by using a logical approach.  Three aspects of process planning are covered: the integration of process planning and design; process planning itself; and the integration of process planning and production management.
Machinery's Handbook | Revised 29th Edition
Erik Oberg et al : Industrial Press
ISBN: 083112900X
Where would we be without Machinerys!