This article is from the Misc Bicycles FAQs, by various authors.
The braze-ons that were put on included two water bottle bosses, pump
peg, cable guides on the top tube, shifter bosses, cable guide on right
chainstay, chain hanger on right seatstay, and rack eyelets on
seatstays. The process was done in several steps since the frame would
need to be tilted at different angles for the various braze-ons. Dave
has various accessory pieces used to hold the braze-ons in place. Most
of them snapped around the tube and then had an arm on them which sat on
top of the braze-on to apply pressure so it would move or fall off.
Silver was used for each braze-on because of the lower temperature
required to work with silver
The first piece done was the brake bridge. First it was tacked in place
so that it wouldn't move while either side was being brazed. Again
small amounts of silver were used and spread between the brake bridge
and the seat stays. The water bottle bosses were next as the bike sat
vertically. These were easy to do, but you had to be sure to use only a
little silver so it wouldn't drip inside. If it did, it wasn't a big
problem since it would roll out the bottom bracket.
To braze the pump peg, the big was tilted with the head tube parallel to
the ground, inside of head tube facing up and again very little silver
because of the small area. Cable guides were down with the top tube
parallel to the ground and the top of the top tube facing upwards. With
the cable guides, they need to be centered along the top tube. For the
shifter bosses, Dave had a little accessory to hold them in place at the
same time. Since the shifter bosses had been mitered already, they sat
squarely against the tube. The cable guide on right chainstay done with
bike upside down; chain hanger with rear triangle parallel to the
ground. For the chain hanger, Dave tilted the chain hanger in just a
little bit so that the chain held on better on the chain hanger.
Finally for the rack eyelets, Dave had another accessory with pegs that
fit through the eyelets on the dropouts to get the right height for the
rack. These were brazed with the seatstays parallel to the ground.