TGS4 - I suggest that you READ the article I sent the link on. http://www.zerofast.com/torque.htm It has a good explanation as to why different grade bolts are torqued differently.
It has to do with the yield strength of the bolt. Here is another handy reference...
There is more to it than just having a chart. It depends on the fastener being used (i.e. bolt grade) and whether or not it is lubricated.
Here is another link to how to calculate the proper torque for a particular fastener: http://www.zerofast.com/torque.htm
If you really want to understand fasteners and learn how to calculate the proper torque for a particular fastener, here is a good starting point: http://gltrs.grc.nasa.gov/reports/1990/RP-1228.pdf
