ALIGNMENT AND POSITIONING USING A LASER CROSS
If you use single cross lasers, you have to take care of the angle between laser beam and surface. Only a cross from a laser in exact perpendicular position to the surface doesn't change its position when the distance to the laser changes. This phenomenom is called parallax error. For cross lasers, it may accect both lines in a different way, depending on the angle.
If there is no way to mount a cross laser perpendicular, like with all drills, you should use two line lasers. They can project from the two sides, resulting in a cross, that doesn't change its position if the working table or the drill change their distance.