I need to fabricate a unequal tee in stainless steel 304 tube. 90 degree joint with tubes of 3/4" and 3", 1.5mm wall thickness. It is only a breather vent so was thinking of drilling smaller than 3/4", say 15mm hole in the 3" and prepping the 3/4" tube with a file to saddle on to the larger pipe, or am I better drilling a 19mm hole and letting it self jig?