[pinhole-discussion] where 2 measure needle diameters?

[Kosinski Family]

Pinhole wizards,
By chance, I photographed a needle and projected it, only to find it had 2 
different angles of taper and the diameter was different everywhere along the 
length of the needle! Checked a lot more needles and found the same thing. The 
question: where on the needle does the diameter from the much published chart 
of needle size / diameter apply? If this chart turns out to be mythological, it 
will only increase my esteem for the inexact art of pinhole photography.
Thanks
Jim