Join Date: Oct 2005
Location: SF, CA
Bikes: Raphael Cycles to be bone.
It's a good idea to drill a pilot hole with a smaller bit, and then go in with the bigger bit. Also, most likely, if you go in from the top, when you break through the bottom you're going to chip out a hunk of granite. It doesnt matter too much, but a way to avoid that would be to drill the pilot hole half way in from the top, measure really really well it's location on the table, and drill the other half of the depth of the table from the bottom, then repeat with the bigger drill bit.
Also, for a 1" threaded rod for your post, you'll want a slightly larger bit.
And try not to breath the dust.