Page 96 - Mechanical Engineer's Data Handbook

APPLIED MECHANICS 85

where: /3= half angle of thread.
Example For /l=30", pe=1.155p.

2.7.6 Tables of friction coentcients

The following tables give coefficients of friction for
general combinations of materials, clutch and brake
materials, machine tool slides and for rubber on
asphalt and concrete.

Coefficient of friction
Materials Lubrication (low pressure)

Metal on metal Dry 0.20 average
Bronze on bronze Dry 0.20
Bronze on cast iron Dry 0.21
Cast iron on cast iron Slightly lubricated 0.15
Cast iron on hardwood Dry 0.49
Cast iron on hardwood Slightly lubricated 0.19
Metal on hardwood Dry 0.60 average
Metal on hardwood Slightly lubricated 0.20 average
Leather on metal Dry 0.4 average
Rubber on metal Dry 0.40
Rubber on road Dry 0.90 average
Nylon on steel Dry 0.3-0.5
Acrylic on steel Dry 0.5
Teflon on steel Dry 0.04
Metal on ice - 0.02
Cermet on metal Dry 0.4

Coefficient of friction Maximum Maximum
temperature pressure
Materials Wet Dry (0°C) (bar)
Cast iron/cast iron 0.05 0.15-0.2 150 8
Cast iron/steel 0.06 0.15-0.2 250 8-13
Hard steel/hard steel 0.05 - 250 7
Hard steel/chrome-plated hard 0.03 - 250 13
steel
Hard drawn phosphor bronze/ 0.03 - 250 10
hard drawn chrome plated steel
Powder metal/cast iron or 0.05-0.1 0.1-0.4 500 10
steel