hole saw
 

you might have to pick up a mandrel for it

try a tile store some stock them. There installers use them all the time

Andrew Sheret sells them

i get mine from princess auto...im going on 30 holes for some of mine so they def do last.


i have all the sizes for all bulkheads and looking at my 3/4" bulkhead bit your going to have to use the 1 1/2" bit.

Thanks there is one near work !