Jerry:
I have seen that tool to center punch the panel. My problem was with two over lapping panels, I could drill them together so the holes were lined up perfect, but if
I did not counter sink them over lapped together they may be slightly off. The counter sink tool had just enough slop to cause a slight misalignment. Not much, but
I'm probably to anal to let it go! LOL

Thanks Mike!

Roger:I have seen protective washers, but not what you mention. There are so many Dzus fasteners offered that I just went with the most popular size, and made the work.