Coefficient of Friction

Extreme care is needed in using friction coefficients and additional independent references should be used.   For any specific application the ideal method of determining the coefficient of friction is by trials.   A short table is included above the main table to illustrate how the coefficient of friction is affected by surface films.  When a metal surface is perfectly clean in a vacuum , the friction is much higher than the normal accepted value and seizure can easily occur.  

......The links below the tables provide further information.

Effect of oxide film etc on coefficient of static friction
Material Clean Dry Thick Oxide Film Sulfide Film
Steel-Steel 0,78 0,27 0,39
Copper-Copper 1,21 0,76 0,74


The level of uncertainty of the information below is indicated by using steel on steel as an example.  Various reference sources provide values similar to the values below.(0,74 Static- 0,42 sliding)   Gieck( 7th ed) provides values of (0,15...0,30 Static - 0,10...0,30 sliding). Concise Metals Data Handbook by J.R. Davis (table 14,1) includes values (0,31 static -0,23 sliding - for steel 1032? on steel 1032?).. The same table includes a value for mild steel on mild steel of 0,62 sliding.




Material 1 Material 2 Coefficient Of Friction Test method
DRY Greasy
Static Sliding Static Sliding
Aluminum Aluminum 1,05-1,35 1,4 0,3    
Aluminum Mild Steel 0,61 0,47      
Brake Material Cast Iron 0,4        
Brake Material Cast Iron (Wet) 0,2        
Brass Cast Iron   0,3      
Brick Wood 0,6        
Bronze Cast Iron   0,22      
Bronze Steel     0,16    
Cadmium Cadmium 0,5   0,05    
Cadmium Mild Steel   0,46      
Cast Iron Cast Iron 1,1 0,15   0,07  
Cast Iron Oak   0,49   0,075  
Chromium Chromium 0,41   0,34    
Copper Cast Iron 1,05 0,29      
Copper Copper 1,0   0,08    
Copper Mild Steel 0,53 0,36   0,18  
Copper Steel   0,8     SPOF
Copper Steel (304 stainless) 0,23 0,21     FOF
Copper-Lead Alloy Steel 0,22   -    
Diamond Diamond 0,1   0,05 - 0,1    
Diamond Metal 0,1 -0,15   0,1    
Glass Glass 0,9 - 1,0 0,4 0,1 - 0,6 0,09-0,12  
Glass Metal 0,5 - 0,7   0,2 - 0,3    
Glass Nickel 0,78 0,56      
Graphite Graphite 0,1   0,1    
Graphite Steel 0,1   0,1    
Graphite (In vacuum) Graphite (In vacuum) 0,5 - 0,8        
Hard Carbon Hard Carbon 0,16   0,12 - 0,14    
Hard Carbon Steel 0,14   0,11 - 0,14    
Iron Iron 1,0   0,15 - 0,2    
Lead Cast Iron   0,43      
Lead Steel   1,4     SPOF
Leather Wood 0,3 - 0,4        
Leather Metal(Clean) 0,6   0,2    
Leather Metal(Wet) 0,4        
Leather Oak (Parallel grain) 0,61 0,52      
Magnesium Magnesium 0,6   0,08    
Nickel Nickel 0,7-1,1 0,53 0,28 0,12  
Nickel Mild Steel   0,64;   0,178  
Nylon Nylon 0,15 - 0,25        
Oak Oak (parallel grain) 0,62 0,48      
Oak Oak (cross grain) 0,54 0,32   0,072  
Platinum Platinum 1,2   0,25    
Plexiglas Plexiglas 0,8   0,8    
Plexiglas Steel 0,4 - 0,5   0,4 - 0,5    
Polystyrene Polystyrene 0,5   0,5    
Polystyrene Steel 0,3-0,35   0,3-0,35    
Polythene Steel 0,2   0,2    
Rubber Asphalt (Dry)   0,5-0,8      
Rubber Asphalt (Wet)   0,25-0,0,75      
Rubber Concrete (Dry)   0,6-0,85      
Rubber Concrete (Wet)   0,45-0,75      
Saphire Saphire 0,2   0,2    
Silver Silver 1,4   0,55    
Sintered Bronze Steel -   0,13    
Solids Rubber 1,0 - 4,0   --    
Steel Aluminium Bros 0,45        
Steel Brass 0,35 0,19    
Steel(Mild) Brass 0,51 0,44      
Steel (Mild) Cast Iron   0,23 0,183 0,133  
Steel Cast Iron 0,4   0,21    
Steel Copper Lead Alloy 0,22   0,16 0,145  
Steel (Hard) Graphite 0,21   0,09    
Steel Graphite 0,1   0,1    
Steel (Mild) Lead 0,95 0,95 0,5 0,3  
Steel (Mild) Phos. Bros   0,34   0,173  
Steel Phos Bros 0,35        
Steel(Hard) Polythened 0,2   0,2    
Steel(Hard) Polystyrene 0,3-0,35   0,3-0,35    
Steel (Mild) Steel (Mild) 0,74 0,57   0,09-0,19  
Steel (Mild) Steel (Mild) - 0,62   FOR
Steel(Hard) Steel (Hard) 0,78 0,42 0,05 -0,11 0,029-,12  
Steel Zinc (Plated on steel) 0,5 0,45 - -  
Teflon Steel 0,04   0,04 0,04  
Teflon Teflon 0,04   0,04 0,04  
Tin Cast Iron   ,32      
Titanium Alloy Ti-6Al-4V(Grade 5) Aluminium Alloy 6061-T6 0,41 0,38     FOF
Titanium Alloy Ti-6Al-4V(Grade 5) Titanium Alloy Ti-6Al-4V(Grade 5) 0,36 0,30     FOF
Titanium Alloy Ti-6Al-4V(Grade 5) Bronze 0,36 0,27     FOF
Tungsten Carbide Tungsten Carbide 0,2-0,25   0,12    
Tungsten Carbide Steel 0,4 - 0,6   0,08 - 0,2    
Tungsten Carbide Copper 0,35        
Tungsten Carbide Iron 0,8        
Wood Wood(clean) 0,25 - 0,5        
Wood Wood (Wet) 0,2        
Wood Metals(Clean) 0,2-0,6        
Wood Metals (Wet) 0,2        
Wood Brick 0,6        
Wood Concrete 0,62        
Zinc Zinc 0,6   0,04    
Zinc Cast Iron 0,85 0,21      
Links to Friction Information
  1. Friction Joint Theory... An informative article
  2. RingFeder ...Keyless Shaft Hub Connection-including relevant friction values
  3. Carbide Depot.. Friction Coefficients
  4. NORD-SKG.. Download manual with various Calculations involving sliding and rolling friction
  5. Supercivilcd Com.. Coefficient of Sliding Friction for various civil Materials
  6. Fastener Design Manual...NASA GRC RP-1228 (9,6 Mbyte pdf file) Includes comprehensive table with friction values.
  7. Physlinks - Coefficient of Friction...A Table of Friction Coefficients
  8. Engineers Edge- Coefficient of Friction...A Table of Friction Coefficients
  9. FrictionCenter- Coefficient of Friction...A Table of Friction Coefficients
  10. School for Champions...Lots of very useful Notes
  11. Investigation of the press fit joints by tribology aspect...A Very Informative paper
  12. Bolt Council...Guide to Design Criteria for Bolted and Riveted Joints.(6,7 Mbyte pdf ).  Info on Slip coefficients (P.82) etc
  13. MD Metric...Datasheet for PTFE
  14. Friction coefficients in "Rail- Wheel" contacts .......Downloadable paper providing very theoretical information
  15. Hypertextbooks _Physics Factbooks.....Physics Factbook .A page inlcuding a number of very good (school) articles on coe-fficents of friction of different materials
  16. 3M Mill Rolls Coef't of Fr'n Study .."...Coefficient of friction values for real applications
  17. NACA Research Memorandum .....Paper Download ..Friction value and surface damage of several corrosion resistant materials
  18. Wear Research Paper .....Paper Download ..A study of the tribological behaviour of polyamide 66 with varying injection-moulding parameters
  19. Fund'ls of Friction and Wear of Automobile Brake Materials .....Paper Download ..Very informative document
  20. Friction in Metal Forming...Chapter 4-aces, Tribology, DimensionalCharacteristics, Inspection and Product Quality Assurance ..
  21. Classical Friction...A very simple and clear description of what determines the coefficient of friction.
  22. 12 Friction...Brown University-Division of Engineering..Very clear document on friction
  23. Rolling Friction...Very useful notes on rolling friction
  24. co-design-5. Mechanics of Screw Threads ...Web page include screw friction values