FSM torque Value

[Wedge]

Hi, everyone I feel kinda dumb for asking this but my mom always said their is no dumb questions so ill go ahead and ask. I am trying to understand what torque numbers do i use in my FSM I have a RB26DETT going in my Z and the FSM states ,for lets say a random bolt, the torque to use is 16-21 (1.6-2.1 , 12-15)N'm (kg-m, ft-Ib)and at the begining of the FSM they state "When X to Y N'm (kg-m, ft-Ib) is indicated, the standard tightening torque is the mean value". I dont understand what the crap that means ? I know i got to convert it in inch/pounds for my Torque wrench that i got it but what number do i use 16n*m or 21n*m or something in between ?

 

Thanks

[Lazeum]

It means you have to shoot in between.

 

In your example: => (16+21)/2 =18.5

 

Make sure to use the appropriate units, in your case:

 

Either 18.5 Nm

 

or 1.85 kg-m (=> (1.6+2.1)/2 )

 

or 13.5 ft-lb (=> (12+15)/2 )

 

 

[Wedge]

Thank you very much ! Merci beaucoup mon ami !

 

Yves.

Edited June 8, 2011 by Wedge

[Tony D]

Do we want to get into why torque is a terribly inaccurate method for measuring tightness? Like 60% of the torque is underhead friction, 25% is thread friction, leaving only about 15% of the torque to actually tension the fastener and clamp the parts together?

 

If not, please play particular attention to the numbers above and draw the conclusion that anti-seize on the threads applied correctly so as not to goop out and get under the head of the bolt is a good thing. But if you get lubricant under the head of a bolt that is being torqued to a specific value, that the value MUST be recalculated as lubrication under the head SIGNIFICANTLY changes how much tension is actually applied to the bolt shank, and can lead to fastener failure!

[Wedge]

Thanks Tony, I always clean up every bolts, nuts and surfaces I torque and try to always use new hardware. I jut want to make sure I follow the RB26 FSM correctly to not overtighten for nothing. I do think that a good clean and new bolt or nut being torqued to FSM spec is safe for my applications.

[Tony D]

The point I was making for the general readership is that by being even a bit sloppy, and 'never' going higher than the specifications in the manual, you can seriously overtorque a fastener, leading to failure.

 

Clean bolts may indeed need to be what it used. In other cases engine oil is called out for lubricant under-head or on the threads. Search and know the lubricant state of the bolt, nut, stud you are tightening!