Here one can see the off-set hole pattern for the tip plugs.I decide to drill the holes into the aluminum first and countersink them to match the screws. I then made a small drill guide to fit into the chamfered hole and drilled a pilot hole into the wooden plugs. This prosess assured yhat the pilot hole s perfectly centered. My experience has been that when drilling a pilot hole first through the aluminum and into the wooded plug and then enlarging the hole in the aluminum skin, the screw is more likely to end up slightly offset. I did the entire oeration on the milling mahine and always slightly rotated the blade to drill perfectly perpendicular holes.
hole pattern laid out for drilling
screws forr tip plug installed. Drill guide is also shown
