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Re: [ST] copper grease and torque settings



>...The nut was loosened then re-tightened to the proper torque. The reading was
>now 
>lower. This was done two more times and each time the pressure was less...


Problem is for something like piston rod head bolts, the type of grease
to apply is specified and more and more it's a torque/angle procedure.
It's the case for the 955i engine.
But most of the cases, nothing is added to the torque spec.
That would probably mean it's for a brand new perfectly clean thread and 
bolt .
Hence for some critical nuts, getting a new one each time is specified.
The surface shape of the thread would probably change after the first 
fastening.

The result of the experiment you're describing is very interesting. I 
would have thought the opposite.
It tends to prove the the surface is damage at each tightening and the 
friction factor gets higher.
It would probably change according to the surface coating (zinc, 
cadmium...) or not of the bolt.

Fred ST 02 BRG
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