Friction and Friction Coefficient

Friction plays an important role in how well screw connections stay tight and secure. The amount of friction, known as the friction coefficient, can change depending on the materials used, how smooth or rough the surfaces are, any coatings or treatments applied, and the type of lubrication used. These factors can make friction increase or decrease, so it’s important to keep the conditions as consistent as possible. If friction is too high or too low, the screw joint may not hold properly or could become damaged. By controlling surface finishes, using the right lubrication, and following proper tightening methods, we can make sure that screw connections remain strong, safe, and reliable.

Friction coeff. class	Range for µG and µK	Typical examples for: Material/surfaces	Lubrication
A	0.04–0.10	metallic, bright-polished black tempered phosphated galvanized coatings such as Zn, Zn/Fe, Zn/Ni zinc laminated coatings	solid lubricants such as MoS2, graphite, PTFE, PA, PE, PI in lubricating lacquers or in pastes wax glazes wax dispersions
B	0.08–0.16	metallic, bright-polished black tempered phosphated galvanized coatings such as Zn, Zn/Fe, Zn/Ni zinc laminated coatings Al and Mg alloys	solid lubricants such as MoS2, graphite, PTFE, PA, PE, PI in lubricating lacquers or in pastes, wax glazes, wax dispersions, greases, oils (as-delivered condition)
		hot-dip galvanized	MoS2, graphite, wax dispersions
		organic coatings	with integrated solid lubrication or wax dispersion
		austenitic steel	solid lubricants or waxes; pastes
C	0.14–0.24	austenitic steel	wax dispersions, pastes
		metallic, bright-polished phosphated	as delivered state (lightly oiled)
		galvanic coatings such as Zn, Zn/Fe, Zn/Ni non electrolytically applied zinc adhesive	none
D	0.20–0.35	austenitic steel galvanic coatings such as Zn/Fe hot-dip galvanized	oil none
E	>= 0.30	galvanized coatings such as Zn/Fe, Zn/Ni austenitic steel Al and Mg alloys	none