Coefficient of Friction (f) for Threaded Pairs
Screw Material	Nut Material
	Steel	Bronze	Brass	Cast Iron
Steel, dry	0.15-0.25	0.15-0.23	0.15-0.19	0.15-0.25
Steel, Machine oil	0.11-0.17	0.10-0.16	0.10-0.15	0.11-0.17
Bronze	0.08-0.12	0.04-0.06	--	0.06-0.09
Source: H. A. Rothbart and T. H. Brown, Jr., Mechanical Design Handbook, 2nd ed. McGraw-Hill, NY, 2006

Thrust-Collar (fc) Friction Coefficients
Combination	Running	Starting
Soft steel on cast iron	0.12	0.17
Hard steel on cast iron	0.09	0.15
Soft steel on bronze	0.08	0.10
Hard steel on bronze	0.06	0.08
Source: H. A. Rothbart and T. H. Brown, Jr., Mechanical Design Handbook, 2nd ed. McGraw-Hill, NY, 2006