On 3/29/2008 3:22 PM Jim Yanik spake thus:

"MiamiCuse" wrote in
:

I need to drill a 5/8" diameter hole through a laminated beam that is
16" deep. This beam is sitting 10 feet above the floor across a room
support part of the roof. So I will be standing on a bench drilling
from below pushing the drill up.

I need this hole to be perfectly vertical as I will be passing a rod
through for a ceiling fan.

What can I do to ensure my drill is perfectly vertical?

I cannot afford to make a mistake and redrill.

get a drill guide;
it's a base with two guide rods,and your drill chuck tightens down on the
guide's own drill chuck shaft.
it's adjustable for 90 deg or angles.
Home Depot and Lowes will have them.

I second that emotion. Have one of those rigs I got 25-something years
ago which has served me well in many similar situations. Not too expensive.