VERY good point Jim and all of what you said is true... given more time, I will reply with a recent story where the torque was calculated on a dry joint and a component change caused the current bolts to stretch! I was called in because we had "bad bolts!" While this can happen - it is VERY rare.I believe what Hank said is correct but I also think his friction percentages look right for a dry fastener. If you lubricate it, those friction loads go down, the clamping loads go up, and the stress in the fastener goes up. So a safe dry torque and a safe lubricated torque are not the same. For some critical applications, the condition of the threads is specified. A washer under the head will also reduce friction under the head.
The time when you determine the amount of torque a bolt can take is when you are designing the connection. You determine the clamping force is appropriate then you find fasteners that can apply that force working well within their capability. In a car engine, you have to worry about dynamic loading of many joints. My point is just that for most of what I do, I am trusting that somebody else determined the safe load on the fastener when they designed the joint and told me the torque to apply.
I believe the OP's intent was a joke...Not sure what the OP's intent is but an accurate way to determine clamping force is to measure bolt extension under load, IMHO. Which makes a good case for using studs and knowing material yield strengths.
Correct - CANNOT fix stupid...Not even good engineers can fix stupid?
Sounds like that there was not much bolt elongation in that application and therefore not much clamping force, yes?
what you are using is a "Torque turn strategy"This all raises a question in my mind about some mechanical fasteners. In years past, I have had applications in both structural steel erection moment connections and engine building where it was specified to tighten the bolt/nut to a specific torque and then turn it an additional xxx degrees. Not sure I understand the purpose of these instructions as it applies to the connection......