Think braze not weld.......ask the guys who really know, but for adding threaded brazeons like for water bottles you might be able to use a MAPP torch.....it did work for me for removing cable guides...... not sure Mapp wold work for day adding threaded eyelets to dropouts for racks and fender mounts
__________________
Life is too short not to ride the best bike you have, as much as you can
(looking for Torpado Super light frame/fork or for Raleigh International frame fork 58cm)