Ramon,
What you suggest, "we added...6, 7, 8 or 5 mils...[to the] specified...final 
hole size...to find the drill size", is very bad practice. How do you know how 
much inner land ring width is left or whether you have break-out? It is the 
drilled hole diameter that needs to be used to determine via reliability [just 
look at all the data and documents, like IPC-TR-578, IPC-TR-579, IPC-TR-486, 
IPC-D-279, they are all in drilled diameters]; it is the drilled hole diameter 
that determines the aspect ratio, it is the drilled hole diameter that gives 
you an idea as to how difficult it is to plate good copper into the hole.
Going with the finished hole diameter was necessary when we used through-hole 
technology, but it is totally outmoded nowadays.

Werner



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