Coefficient of Friction Equation and Table Chart

Design Resources | Friction Design Data

The frictional force for Static Friction can be expressed as:

Fmax= μ Fn

where

Fmax= Frictional force (N, lb)
μ = static (μ s ) or kinetic (μ k ) frictional coefficient
Fn = Applied Normal force (N, lb)

The frictional force for Dynamic Friction can be expressed as:

For an object pulled or pushed horizontally, the normal force - N - is simply the weight :

N = m g

Where:

m = Mass (kg, slugs )
g = Gravity (9.81 m/s2 , 32 ft/s2)

Material Against Material Static Coefficient of Friction
Dry Contact Lubricated Contact

Aluminum

Aluminum 1.10 -1.35

.30

Aluminum-Bronze Alloy Steel .46 -
Aluminum Steel .61 -
Brake (Composite) Cast Iron .40 .21 (wet)
Brass Steel .50 .19
Brass Cast Iron .28  
Brick Wood .60 -
Bronze Cast Iron .21 -
Bronze Sintered Steel - .12
Bronze Steel   .16
Cadmium Cadmium .50 .05
Cadmium Chromium (Chrome) .40 .35
Cadmium Steel, Mild .46  
Carbon Carbon .15 .12 - .14
Carbon Steel .14 .12 - .14
Cast Iron Cast Iron 1.1 .08
Cast Iron Copper 1.05 -
Cast Iron Oak Wood .485 .08
Cast Iron Steel .40 .21
Cast Iron Zinc .85 -
Chromium (Chrome) Chromium (Chrome) .41 .34
Colbalt (70°C) Cobalt .3 -
Concrete Rubber 1.0 .30 (wet)
Concrete Wood .62 -
Copper Cast Iron 1.05 -
Copper Copper 1.00 .08
Copper Glass .94 -
Copper Steel .53 -
Copper-Lead Alloy Steel .22 -
Cork Iron .35 -
Diamond Diamond .10 .05 - .10
Diamond Metal .10 - .15 .10
Glass Glass .90 - 1.0 .10 - .60
Glass Metal .50 - .70 .20 - .30
Glass Nickel .78 .57
Graphite Graphite .10 .10
Graphite Steel .1 .1
Horseshoe Concrete .67 -
Horseshoe Rubber .28 -
Ice Wood .05 -
Ice Steel .04 -
Iron Iron 1.0 .15 -. .20
Lead Cast Iron .41 -
Leather Iron .3  
Leather Wood .30 - .40 -
Leather Metal .60 -
Leather (Greasy) Iron .2 - .25  
Magnesium Magnesium .60 .079
Masonry Brick .65 -
Nickel Nickel .70 .28
Nylon Nylon .15 - .25 -
Oak Oak .61 -
Paper Cast Iron .19 -
Phosphor Bronze Steel .35 -
Platinum Platinum 1.20 .25
Plexiglas Plexiglas .80 .80
Plexiglas Steel .40 - .50 .40 - .50
Polyethene Steel .2 .2
Polystyrene Polystyrene .50 .50
Polystyrene Steel .30 - .35 .30 - .35
Rubber Rubber 1.15 -
Rubber Asphalt .9 -
Rubber Concrete .6 -
Rubber (60 A Belt) Stainless Steel 316 .64 -
Rubber (60 A Belt) Rubber (40 A Belt) .62 -
Rubber (60 A Belt) Rubber (60 A Belt) .73 -
Rubber (60 A Belt) Tool Steel .86 -
Rubber (60 A Belt) Tungsten Carbide .62 -
Rubber (60 A Belt) UHMW .56 -
Rubber (60 A Belt) Urethane 50 .60 -
Rubber (60 A Belt) Urethane 80A .70 -
Rubber (60 A Belt) Urethane .67 -
Silver Silver 1.40 .52
Skin, Human Metals (63 Ra) .9 -
Steel Steel .80 .16
Teflon Steel .04 .04
Teflon Teflon .05 - .20 .04
Tin Cast Iron .31 -
Tire, Rubber Asphalt .71 -
Tire, Rubber Grass .36 -
Tungsten Carbide Steel .40 - .60 .10 - .20
Tungsten Carbide Tungsten Carbide .20 - .25 .12
Wood Wood .25 - .50 .20
Wood Metals .20 - .60 .20 (wet)
Zinc Zinc .60 .04

Static friction is friction between two or more solid objects that are not moving relative to each other. For example, static friction can prevent an object from sliding down a sloped surface. The coefficient of static friction, typically denoted as μs , is usually higher than the coefficient of kinetic friction.

Material

Sliding

Dry

Lubricated

Aluminum on aluminum

-

-

Canvas belt on rubber lagging

-

-

Canvas belt, stitched, on steel

0.20

0.10

Canvas belt, woven, on steel

0.22

0.10

Cast iron on asbestos, fabric brake material

0.35-0.40

-

Cast iron on brass

0.30

-

Cast iron on bronze

0.22

0.07-0.08

Cast iron on cast iron

0.15

0.06-0.10

Cast iron on copper

0.29

-

Cast iron on lead

0.43

0.13-0.36

Cast iron on leather

-

0.07-0.20

Cast iron on oak (parallel)

0.30-0.50

-

Cast iron on magnesium

0.25

0.133

Cast iron on steel, mild

0.23

-

Cast iron on tin

0.32

-

Cast iron on zinc

0.21

-

Earth on earth

-

-

Glass on glass

0.40

-

Hemp rope on wood

0.40-0.70

-

Nickel on nickel

0.53

0.12

Oak on leather (parallel)

0.30-0.50

-

Oak on oak (parallel)

0.48

0.16

Oak on oak (perpendicular)

0.32

0.07

Rubber tire on pavement

0.75-0.85

0.5-0.7*

Steel on ice

0.01

-

Steel, hard, on babbit

0.33-0.35

0.05-0.16

Steel, hard, on steel, hard

0.42

0.03-0.12

Steel, mild, on aluminum

0.47

-

Steel, mild, on brass

0.44

-

Steel, mild, on bronze

0.34

0.17

Steel, mild, on copper

0.36

0.18

Steel, mild, on steel, mild

0.57

0.09-0.19

Stone masonry on concrete

-

-

Stone masonry on ground

-

-

Wrought iron in bronze

0.18

Wrought iron on wrought iron

0.44

0.08-0.10

 

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