Oh, Nate, this is gonna be fun...

Before we get going, everybody go read "bolt science" faq's, so we are all at the same state of confusion...

For starters, after you subtract thread friction and underside of the bolt head friction on the washer, I think you are left with something like 12% of the twisting force actually goes to preloading the fastener for a 12mm diameter. The variable list is very large, shaft diameter, fastener material, thread pitch, thread form, thread tolerances (root, crown, axial, lineal), desired clamping load. It's the number of variables that caused fastener engineers to start using angle of rotation instead of raw torque. You preset the fastener to a lower than specified torque, then rotate it a calculated angle to achieve the desired fastener preload.