Old as Dirt!
A slip neighbor of ours has purchased replacement Acrylic hatch lenses, one of which has a cut-out for a vent. The vent itself is held in place with 3 machine screws that, in the old lens, screw into threaded holes in the lens that the replacement lens is not furnished with. (Note that the screw holes do not go all the way through the lens and are tapped for 6mm machine screws.) So he needs to drill and tap new screw holes and has asked my help. I am not certain how one goes about doing that and I surely don't want to goof up his $100+ lens. I will appreciate any information/instruction from anyone that has previously done a project like this successfully. (I did tap Google for info on the process but thought the collective here might offer some helpful insights.)