The present invention is directed to a portable drill press apparatus for drilling a bore perfectly perpendicular to a surface. This apparatus includes a horizontal base plate having an enlarged aperture and a horizontal adjustment plate having an adjustment plate aperture. The adjustment plate is parallel to and releasably connected to the base plate by a plurality of releasable fasteners extending through a plurality of adjustment slots in the adjustment plate. A plurality of guide bolts extends vertically from the adjustment plate through a horizontal guide plate, the guide plate being parallel to the adjustment plate and slidable along the plurality of guide bolts. The guide plate has a guide plate aperture. A vertical back plate interconnects the guide plate and at least one drill clamp, the guide plate and drill clamp extending parallel to each other. The drill clamp has a variably-sized drill aperture for clamping a portable drill.