The critical load curves for the bolts shown in the static diagrams relate on principle to strength class 10.9 bolts. The clamping length l_k is assumed to be 5 · d with a preload of 70% of the yield point.

For bearings without indicated bolt curves, the entire load capacity range below the critical load curves is covered by strength class 10.9 bolts.

Analysis of the bolt curves must be based on the maximum load without factors.

Our technical quotation will show the number of bolts, strength class and required prestress for the bearing concerned and the loads indicated. Unless mentioned otherwise, the following shall be assumed:

1. The axial load F_a is supported, i.e. the axial operating force F_A from the axial load does not exert any tensile stress on the bolts.




Axial load "compressive"



Axial load "suspended"


2. The bolts are equispaced around the hole circles.
   
   
3. The mating structures are meeting our technical requirements.
   
   
4. Bearing and mating structures consist of steel.
   
   
5. No resin grouting provided.
   
   
6. The clamping length l_k is at least 5 · d for bearings with a fully annular cross section and at least 3 · d for profiled bearings, e.g. KD 210 type series.
   
   
7. There are at least six free threads available in the loaded bolt section.
   

Where deviations in these conditions occur, prior consultation with us will be required.

In order to avoid prestress losses due to creeping, the surface pressures (see rough determination of the surface pressure) in the contact areas between bolt head and nut/material of the clamped parts should not be exceeded.

The selected product and strength classes of bolts and nuts must be guaranteed by the manufacturer to DIN/ISO standards.

The angularity between support and bolt/nut thread axles must be checked.

Pitch errors which will falsify the tightening torque and lead to lower bolt prestress forces, especially if the reach is > 1 · d, must be avoided.

Table: Table: Minimum engagement for blind hole threads. Applies to medium tolerance class (6 H).

Table 4 (tightening torques) does not show any tightening torques for bolts > M 30, as experience has shown that their friction coefficients vary too much. These bolts should preferentially be tightened using a hydraulic tension cylinder, see Prestressing of fastening bolts (Stretch method).

The increased space requirement for bolt head, nut, and tightening tool must be taken into account as early as possible during the design phase. The thickness of the washer must be adapted to the bolt diameter. Observe plane-parallelism.