To double the Area -- D2 = 2.8 x D1

D1 is extisting size - measure with a drill bit
D2 new size for double area

Thie is actually a bit under, actually -- R2 = sqrt(2) x R1 ( note these are radius and need to be doubled for diameter)

But by the time the bit gets done ripping and gougeing that soft metal it will probably be close enough.

This comes from doing a little algebra on the formula for the area of a circle.


Steve