With a plywood template centered over the hole and a pattern (top bearing)
router bit like this, http://www.rockler.com/product.cfm?page=5411  one
could do a pretty clean job.
Don
----- Original Message -----
From: "Jake de Villiers"
>A 1/2" shankcarbide router bit works very well on aluminium, but its not a
> job for a neophyte!  =)
>
> On Mon, Feb 1, 2010 at 11:13 AM, Sudhir Desai
> <sudhir.desai@gmail.com>wrote:
>
> 1984 Vanagon GL
> 1986 Westy Weekender "Dixie"
>
> Crescent Beach, BC
>
> www.thebassspa.com
> www.crescentbeachguitar.com
> http://subyjake.googlepages.com/mydixiedarlin%27
>
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