| Symbol | μTmin |
|---|---|
| Unit | - |
| Attribute-ID | vdi_2230_minimum_coefficient_of_friction |
| Numeric ID | 12133 |
| Value Type | PMDouble |
The minimum friction coefficient in the interface µTmin is required to achieve the required minimum clamp load FKQ (R2) of a bolted joint, for the transmission of shear force or torsion.
| Material comination (Generally the state following machining) |
Static friction coefficient µT in the state | |
| dry | lubricated | |
| Steel - steel/cast steel (general) | 0.1 to 0.3 | 0.07 to 0.12 |
| Steel - steel; cleaned | 0.15 to 0.40 | - |
| Steel - steel; case-hardened | 0.04 to 0.15 | - |
| Steel - GJL | 0.11 to 0.24 | 0.06 to 0.1 |
| Steel - GJL; cleaned | 0.26 to 0.31 | - |
| Steel - GJS | 0.1 to 0.23 | - |
| Steel - GJS; cleaned | 0.2 to 0.26 | - |
| GJL - GJL | 0.15 to 0.3 | 0.06 to 0.2 |
| GJL - GJL; cleaned/degreased | 0.09 to 0.36 | - |
| GJS - GJS | 0.25 to 0.52 | 0.08 to 0.12 |
| GJS - GJS; cleaned/degreased | 0.08 to 0.25 | - |
| GJL - GJS | 0.13 to 0.26 | - |
| Steel - bronze | 0.12 to 0.28 | 0.18 |
| GJL - bronze | 0.28 | 0.15 to 0.2 |
| Steel - copper alloy | 0.07 to 0.25 | - |
| Steel - aluminium alloy | 0.07 to 0.28 | 0.05 to 0.18 |
| Aluminium - aluminium | 0.19 to 0.41 | 0.07 to 0.12 |
| Aluminium - aluminium; cleaned/degreased | 0.10 to 0.32 | - |
Note: Due to the large number of variables influencing the coefficient of friction, only typical ranges can be provided here. In the specific instance the minimum coefficient of friction need not correspond to the lower limit of the range in question and it may be necessary to carry out experimental analyses. This is also recommended for measures to increase the coefficient of friction.
Table from: VDI 2230 Part1, VDI Verlag Düsseldorf, 2015, p. 115, "Table A6. Approximate values for static friction coefficients at the interface."