Giant 5' diameter hole saw.
https://diqn32j8nouaz.cloudfront.net...ge_holesaw.jpg
In action, 4:55 video:
https://www.youtube.com/watch?v=0GeptRIHYvw
Previously:
https://www.homemadetools.net/forum/...737#post102333
https://www.homemadetools.net/forum/...229#post101052
https://www.homemadetools.net/forum/...734#post124027
https://www.homemadetools.net/forum/...907#post102827
https://www.homemadetools.net/forum/...174#post138381
https://www.homemadetools.net/forum/...871#post129275
