R. Pierce Butler wrote:

I wouldn't want to use a 4" bit in a hand held drill if I wanted a
precise hole.

I'd use a saw to rough out the hole, then a router with a guide bushing
and template.

I used a 3" bit in a hand held drill and the holes were quite accutate. I
think I will post a picture of what I was drilling.


I used upto a 6" hole saw for such things, clamp a sheet of metal top
and bottom to help guide (pilot the top one) and support edges, worked a
treat everytime.