Hi all!

Does anybody know what the proper use is for nuts and bolts with serrated flange heads?  If I understand it correctly, they were developed to eliminate the need for washers and make installation simpler.  However, I'm wondering how they're "gripping" power compares to a  typical hex nut, bolt & lock washer combination when subjected to the same levels of vibration?  Does anybody have any real comparison data or know where to look?  The manufacturers of flange nuts/bolts that I've checked with don't seem to know.  Also, on certain pieces of equipment, I've noticed that some manufacturers only use flange nuts when paired with a flange bolt while others use a typical hex bolt with a flange nut.  Is the hex bolt/flange nut combination considered acceptable, or is it just done to save a few bucks?  Does it matter what material thicknesses are being bolted together when using flange nuts and bolts?  As you can see, I have many questions on this subject. 

If you have some knowledge or information, please post. 

Thanks!