Friction Coefficient

Written by Jerry Ratzlaff. Posted in Fluid Mechanics

Friction coefficient or "Coefficient of Friction" is the ratio between two contacting surfaces and the frictional force that resists the normal force of the object.

formula

\( \mu =   \frac {F_a}{F_n}\)

Where:

\(\mu\) (Greek symbol mu) = friction coefficient

\(F_a\) = applied force

\(F_n\) = normal force

materials table

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.

Material 1Material 2Coefficient of Friction
DryGreasy
StaticSlidingStaticSliding
Aluminum Aluminum 1.05 - 1.35 1.4 0.3 -
Aluminum Mild Steel 0.4 - - -
Brake Material Cast Iron - - - -
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 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 - -
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 (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 - -
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 - -