I did mine with a drill.  I checked with a wheel repair guy first and was
going to pay him, and he said a drill would work fine.  Because there is a
hole already, the drill tends to self-center.  Also the cone that the lug
fits in remains so that tends to center the lugs.  The Mercedes alloy is
pretty soft, so the drill caught a couple times-so you want to avoid
pushing.  Also want to keep the drill as verticle as possible.  But it
seemed easy enough.  I put two of the wheels on the front and drove around
and they seemed in balance fine. I needed rear studs for the rear so I have
never gotten around to finishing getting them on.

>From: Agent99 <email99@BELLSOUTH.NET>
>Reply-To: Agent99 <email99@BELLSOUTH.NET>
>To: vanagon@GERRY.VANAGON.COM
>Subject: Drilling 14mm holes in alloy rims?
>Date: Thu, 22 Dec 2005 01:26:08 -0500
>
>Would anyone care to share their experiences in enlarging 12 mm holes to
>14 mm for lug bolts/studs in aluminum rims.  Is this something that can
>be done with a hand held electric drill with success or does it require
>a machine shop to do it accurately enough to have true running wheels?
>Has anyone screwed up a rim while trying to enlarge the lug holes?
>
>You can reply either to the list or pmail me directly if you like.
>
>Thanks,
>
>Ed