Hole saw, is a possibility, A Forstner bit (spelling?) is another
possibility, but as the hole saw can not be enlarged. Finding a 14mm
Forstner bit may be difficult but they cut a very clean hole with a flat
bottom and once centered they stay put without drifting unless you want to.

A Forstner bit does not like a pilot hole, just a smal dimple to locate the
small tip.

On the other hand you may want to sacrifice a cheap 9/16 router bit by
grinding it down to 14mm, only a couple of lics on the grinder. You may
even go a little conical.

Now for the suggestion you do not want to hear. There is always epoxy glue
to fill up the gaps.
This is a challeging job, hope it goes well.

MG


"Joe Bobst" wrote in message
...
my largest twist-drill bit (1/2'') and it tore the sidewall

1/2 " holesaw, maybe?

Joe