The science of nuts and bolts is a lot more technical then I originally thought. Probably the reason for the fine threaded bolts is that they can be tightened a lot snugger then a course threaded bolt.
Also they need to match up the right grade of bolt and nut. A mismatched bolt or nut will create a weak link.
I am sure others will come along with more information.
Good luck on your project.
Jim
