Just to amplify pedro's reply

If you don't know the torque spec to tighten a bolt, and you have a digital torque wrench, can you "figure out" what the torque value is by loosening the bolt with the digital wrench and reading what value it was to move the bolt?

BTW, I just received my Brownline digital torque wrench...... and I have an active imagination.... oh oh... bad things about to happen.......

Hmmmm...

Peace
Bruce in Philly

Torque wrenches shouldn't be used for loosening.
When you tighten a bolt, part of the final procedure is stretching the bolt a bit so that friction grabs and holds the threads in place.
Loosening it will take more force than tightening did in the first place. Plus some oxidation mar occur which will add to the force needed to loosen the bolt.
Happy Porscheing,
Pedro

Pedro Bonilla
1998 Boxster 986 - 311,000+ miles: [www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

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I'm no expert but I did spend a lot of time hanging around a diesel engine rebuild shop. I have seen mechanics measuring "breakaway torque" when analyzing failures. I'm not sure what that revealed. But when they wanted to know the torque of an existing bolt they would mark the position, loosen it and then retighten to the mark while measuring the required torque. Presumably this gave the bolt the same amount of stretch it had before and therefore required the same torque. If the bolt had been overtightened to the point of plastic deformation this wouldn't work.

Ever have a rusted bolt that just wont budge?

It wasn't put n that tightly, was it?

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

Quote
Bruce In Philly (2000 S Boxster, now '09 C2S)
If you don't know the torque spec to tighten a bolt, and you have a digital torque wrench, can you "figure out" what the torque value is by loosening the bolt with the digital wrench and reading what value it was to move the bolt?

BTW, I just received my Brownline digital torque wrench...... and I have an active imagination.... oh oh... bad things about to happen.......

Hmmmm...

Peace
Bruce in Philly

Try to find out what the torque spec is for every fastener, it listed in Porsche manuals and bentleys, etc. When you have no spec, use this chart as a guide for torques. If you are putting a steel bolt into aluminum, use the lower values.

[www.swtc.edu]