FWIW, the original sights on the Colts, including the 51 and 60, were neither screwed in nor soldered, they were just pressed in. The 51 Navy cone sight was installed by dropping a short length of soft brass into the hole, then pressing it in with an arbor press that had a hole in the ram shaped like the cone in reverse. Drop in the brass, bring down the ram, lean on the handle, and you have a front sight!
Jim