Didn't have a big enough hole saw, and my mill is still in refurb mode, so had to do it the hard way. After laying out the diameter of the hole, and the circle where the 50 #30 holes would be drilled, the spacing was laid out and each mark center punched. After the #30 holes were drilled, they were enlarged with a #16 bit, and the webs were removed with a cutoff wheel.
The ragged edge was cleaned up with a carbide burr and emery paper. The hole isn't perfect but it's good enough for the final op which will weld the tank extension over it.
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