Don't believe you'll be able to find a router bit long enough to get
through a 4X4. As Edwin suggests rent the proper tool.

On 21 Dec 2004 23:30:06 -0800, wrote:

My wife and I are building some decks on my house using ipe wood for
the deck boards and railings. Those who are familiar with ipe know
that it is VERY heavy and dense; one must pre-drill for every screw and
bolt. Our 18-volt cordless (Ryobi) drill has been great for drilling
little holes for the #10 screws in the deckboards and in the railings,
but it is nowhere nearly up to the task of drilling 1/2 inch holes
through ipe 4X4's for the lag bolts on the railing posts.