The proper size tap drill for a 6-32 tap is a #36 drill or about .106". A 4-40 is a #44 drill. I have been using a 1/8" pop rivet with a long drill inside to locate my holes for a while. They are mostly for 4-40 bolts though. I also do one hole with the rivet/locater thing by hand to just make a dimple, then drill the rest of the way through, and tap it. I bolt it in place, and then spot the next hole, drill and tap it, and put the bolt in. then spot the rest and finish up.. I found it best to use a drill press after many years of trial and error, this is about the best way I know of. The rivet thing is just a redneck type of the Great Pains setup.