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Bolts
General
General
Deviating tolerance classes require appropriate screw depths to be assigned.
d - exterior threads-Ø [mm]
- Bolts with metric ISO threads (regular thread)
P - pitch of the thread [mm]
- Up to M 30 have a d/P < 9
- > M 30 have a d/P > 9
Estimated determination of the surface pressure
Under the head contact or the nut contact area
Condition:
p = (FM / 0.9) / Ap ≤ pG
FM - Assembly preload force of the selected bolt [N]
Ap - Contact area or nut (screw head) [mm2]
pG - Surface pressures [N/mm2] for the pressed parts
Here, the reduced contact area due to hole chamfer and seating plate must be taken into consideration.
Ap = (π / 4) · (dw 2 - dh 2)
for dh > da
dh - hole diameter
da - inner diameter of the head contact surface
dw - outer diameter of the head contact
Table 3 : pG Surface pressures [N/mm2] for the pressed parts
| Material | pG Surface pressures |
|---|---|
| St 37 | 260 N/mm2 |
| St 50, C 45 N, 46 Cr 2 N, 46 Cr 4 N | 420 N/mm2 |
| C 45, profile rolled (KD 210) | 700 N/mm2 |
| C 45 V, 46 Cr 4 V, 42 CrMo 4 V | 700 N/mm2 |
| GG 25 | 800 N/mm2 |
Table 3 : pG Surface pressures [N/mm2] for the pressed parts
| Material | pG Surface pressures |
|---|---|
| St 37 | 260 N/mm2 |
| St 50, C 45 N, 46 Cr 2 N, 46 Cr 4 N | 420 N/mm2 |
| C 45, profile rolled (KD 210) | 700 N/mm2 |
| C 45 V, 46 Cr 4 V, 42 CrMo 4 V | 700 N/mm2 |
| GG 25 | 800 N/mm2 |
Tightening torque
The tightening torque is based on many factors, particularly on the coefficient of friction in the thread and on the head or nut contact area.
For an average coefficient of friction of μG≈μK = 0.14 (lightly oiled thread and head contact area), the tightening torque, MA for preloading, FM is specified for the hydraulic torque drivers.
Taking into account a spread of ± 10%, the installation torque, MA' is determined for the dynamometric key.
Clamping forces and tightening torques for screws with DIN 13 regular thread for μG≈μK = 0.14
Strength class in accordance with DIN/ISO 898: 8.8 10.9 12.9
Table 4: Clamping forces and tightening torques for bolts with DIN 13 regular thread for µG ≈ µK = 0.14
| Strength class in accordance with DIN/ISO 898 | 12.9 | ||||
|---|---|---|---|---|---|
| Yield strength Rp 0.2 N/mm2 | 1100 | ||||
| Metric ISO thread | Tension cross-section | Core cross section | Clamping force | for hydro. + electro. Md-bolts | for Md'-*key |
| DIN 13 | AS mm2 | A3 mm2 | FM kN | MA Nm | MA' Nm |
| M12 | 84.3 | 76.2 | 61 500 | 160 | 144 |
| M14 | 115 | 105 | 84 400 | 255 | 230 |
| M16 | 157 | 144 | 115 700 | 395 | 356 |
| M18 | 193 | 175 | 141 000 | 549 | 495 |
| M20 | 245 | 225 | 181 000 | 773 | 696 |
| M22 | 303 | 282 | 225 000 | 1057 | 951 |
| M24 | 353 | 324 | 260 000 | 1329 | 1196 |
| M27 | 459 | 427 | 342 000 | 1959 | 1763 |
| M30 | 561 | 519 | 416 000 | 2662 | 2396 |
| M33 | 694 | 647 | 517 000 | Determine the bolt through strain measurement | |
| M36 | 817 | 759 | 608 000 | ||
| M39 | 976 | 913 | 729 000 | ||
| M42 | 1120 | 1045 | 830 00 | ||
| M45 | 1300 | 1224 | 968 000 | ||
| M48 | 1470 | 1377 | 1 090 000 | ||
| M52 | 1760 | 1652 | 1 312 000 | ||
| M56 | 2030 | 1905 | 1 5 11 000 | ||
| M60 | 2360 | 2227 | 1 764 000 | ||
* = MA changes in the event of deviating µG or µK