Gang,
Fillet brazing frames is an artform in itself. Fillet brazing sort of comes in two parts. The brazing itself is part one. There are some brazers who through enough practice are so skillful at laying down the brass that they look almost finished when done brazing. I've seen this level of skill from several builders but I can only remember studying my tandem that Ross Schafer from Salsa brazed for me. It was almost a shame to take a file to those joints. I have built several fillet brazed bikes but my fillets are not quite as surgical.
Part two is how the fillet is filed after brazing. A good fillet is easy to file whareas a poor one will yeild an uneven looking radius in various places. Also could be full of small pinholes from poor control of the temp. of the brass. I concentrate on getting good penetration of the brass and laying down enough brass to get a beautiful joint once filed. If one looks closely at old Taylors and such the filing is not all that good on some of them. An even consistant radius with no undercutting or filemarks are the hallmarks of a nice fillet joint, assuming the brass penetrated properly. Many beautiful things have and will be built using fillet brazing techniques. Too much fillet brazing can bet boring for a lug person like myself; but a nice job now and again can be a real treat.
Brian Baylis La Mesa, CA Will be using some fillet brazing techniques on my French-style "AeroTour" lugs in combination with standard silver brazing.