Torque specification with angle of rotation

Explanation

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In the automotive industry and in engine construction, you will often hear the specification torque [Nm] and angle of rotation [°] for screw connections. For a screw connection with a torque and angle specification (e.g. 100 Nm + 90°), the screw is first tightened to 100 Nm using a torque wrench and then turned a further 90° (quarter turn).
The 100 Newton meters represent the initial torque, which you then increase with the angle of rotation of 90° in this example.

1) Why torque and angle of rotation?

The Rotation angle specification is relevant because the required preload force can be achieved much more precisely with its help. With the angle of rotation method, the yield point force of the screw is exceeded. For this reason, this method is often used for Safety-relevant screw connections used. It is also another Monitoring valuewith which you can better check the screw connections.

The specification of the angle of rotation in connection with the torque is also called Further rotation angle called. The screw is tightened to a torque and then turned further by the specified angle. One advantage of this process is that the Retightening the screw is no longer necessary is.

Combined tightening method for screw connections, torque with angle of rotation
Example of characteristic curve for tightening method with angle of rotation

2) Torque table with angle of rotation

In the following table you will find the Required torques with angle of rotation for screws from M12 to M36. These values can be used if no further details are given for the required screw connection. Data according to DIN 18800-7: 2008-11 "Combined method".

DimensionsM12M16M20M22M24M27M30M36
Preload force
F = 0.7 x fub x As [kN]
59110172212247321393572
Pre-tightening torque
Ma [Nm]
7519034049060094012402100
Total thickness "t" of the parts to be joined
(including all lining plates and disks)
d = screw diameter
Further rotation angleFurther rotation dimension
1
t < 2d601/6
22d = 6d901/4
36d =10d1201/3
These are only examples of manufacturer specifications. The exact angle of rotation should be determined in theory by testing

3) Example: Tighten the collar screw of the drive shaft

In this example, we take the Collar bolt of the drive shaft from a BMW F30. This screw should be 210 Nm + 90° be consulted.

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When replacing the tension strut on a BMW all-wheel drive, the collar bolt of the drive shaft must be loosened. After the repair, a new collar bolt is required and this should be tightened to 210 Nm and 90°.

First, tighten the screw onto the Required torque [Nm] on. In this case, set the torque wrench to 210 Nm. If your torque wrench does not go that high, the maximum is also sufficientwhich you have at your disposal.

Torque wrench set to the maximum in this example
Setting the torque [Nm] for a torque wrench (pre-tightening torque)

Next, try using the longest ratchet (ratchet) you have, the screw around 90° (quarter turn) further. Mark the screw beforehand, to better track the quarter turn.

If you need more force, you can lengthen the ratchet to apply more force (leverage).

Observe the angle of rotation as precisely as possible
Marking on the screw to track the angle of rotation

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