Portable Multi-Angle Drill Guide with Drill Chuck

The bottom of the chuck at maximum height is 6 5/8" from the bottom of the base. With the springs and depth lock installed the guide travels 6". If springs and depth lock are removed the bottom of the chuck could reach about 3/4" below the base. Your drill bit will need to extend from the chuck between 6" and 6 5/8". 7/8" of the drill bit will be inside the chuck. So your drill bit must be between 6 7/8" and 7 1/2" to drill 6" deep holes in one step. Or you could use a shorter then a longer bit to drill in 2 steps. You may not need the guide for the second step with a longer bit since the hole will guide the bit. I would practice on scrap first to make sure it's acceptable. Also I would remove the rubber feet and clamp the drill guide to your workpiece. On a deep hole the rubber feet compress enough when clamped to change the angle slightly.

Yes you can lock in an angle. I haven't tried it yet but would definitely clamp the drill guide to the workpiece and probably practice a a scrap piece first.

I can't see how you could replace the existing chuck with a 1/2" chuck.

I don't see any reason you couldn't as long as you can hold or clamp the drill guide in place.

The hole on the base of the drill guide is 2 7/8" so a 3" bit would not work.

Yes, that is what I used.

Depending on which side of the drill guide is against the wall about 2 1/2" or 2 5/8" from the center of the drill bit.

I would have preferred a 1/2" chuck but could not find one on a drill guide. I live nowhere near you but I was not able to find any drill guide in stock anywhere close so ordered it from Home Depot. It came pretty quick. I just saw how old this question is so answering it seems pretty silly but whatever.

The depth of travel is about 6.0" with the springs installed. If you remove the springs and depth adjustment add about 1.5" which is about 7/8" past the bottom of the base.