Testing is fun and you can learn a lot. Have you looked at the published ratings?
http://www.cardinalcomponents.com/as...properties.pdf
Like Clint mentioned fasteners under 1/4" will generally be measured in in/lbs rather than f/lbs.
Understand that the torque charts are a guide for a properly torqued fastener. These are within the working limits of the fastener. As you've discovered the shear point is quite a bit higher and material plays a big part.
I would think that if your seeing fastening system failures it is likely due to poorly designed joints and/or improper fastening system selection. Of course that's assuming proper installation.
