A spoon bit will ream a hole out nicely, but I don't have one that big.

I would be tempted to use a forstner bit in a bit brace. 

I've never tried this on a bench, so I'm speculating.

Gary Katsanis
Albion New York, USA
(where we are having a very welcome thaw)

---- Claudio DeLorenzi  wrote: 

=============
I’m trying to remember exactly how I em-biggened some d’oh-(forehead
slap)-too-small holes on one of the past builds...

 --- info about a tailed apprentice snipped out ---