| Symbol | μKmin |
|---|---|
| Unit | - |
| Attribute-ID | vdi_2230_minimum_coefficient_of_friction_in_the_head_bearing_area |
| Numeric ID | 12210 |
| Value Type | PMDouble |
The minimum coefficient of friction in the head bearing area µKmin is used to determine the required tightening torque (R13).
| Friction coefficient class |
Range for µG and µK | Selection of typical examples for | |
| Material/surfaces | Lubricants | ||
| A | 0.04 bis 0.10 | metallically bright black oxide phosphate galvanic coatings such as Zn, Zn/Fe, Zn/Ni Zinc laminated coatings | solid lubricants, such as MoS2, graphite, PTFE, PA, PE, PI in lubricating varnishes, as top coats or in pastes; liquefied wax; wax dispersions |
| B | 0.08 bis 0.16 | metallically bright black oxide phosphate galvanic 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 varnishes, as top coats or in pastes; liquefied wax; wax dispersions, greases; oils; delivery state |
| hot-galvanized | MoS2; graphite;wax dispersions | ||
| organic coatings | with integrated solid lubricant or wax dispersion | ||
| austenitic steel | solid lubricants or waxes; pastes | ||
| C | 0.14 bis 0.24 | austenitic steel | wax dispersions, pastes |
| metallically bright phosphated | delivery state (lightly oiled) | ||
| galvanic coatings such as Zn, Zn/Fe, Zn/Ni Zinc laminated coatings adhesive | none | ||
| D | 0.20 bis 0.35 | austenitic steel | oil |
| galvanic coatings such as Zn, Zn/Fe; hot-galvanized | none | ||
| E | ≥ 0.30 | galvanic coatings such as Zn/Fe, Zn/Ni austenitic steel Al, Mg alloys | none |
Table from: VDI 2230 Part 1, VDI Verlag Düsseldorf, 2015, p. 114, "Table A5. Friction coefficient classes with guide values for different materials/surfaces and lubrication states in bolted joints."