as has been already posted, the pins are there as surrogate holding devices (as would be a small braze tack...) so you can take an assembled-but-not-brazed frame and then torch it freehand. the pins (and tacks) do not replace the need for some kind of fixture or precision holding device; they enhance them by allowing the effbuilder to use them to get the pipes and joints in plane and to the correct geometry and then braze it all without the confinements of q/r clamps, aggressive v-blocks, and contorted positions that arise from jigs that have blind spots. the essence of all this is that the metal needs/wants to expand and contract, and holding the pipes rigid works against of the quality of the build. a fixture is responsible for the design being true to the maker's original concept, but the care with which all the material is loaded up reflects his experience and vision for the finished product. these added steps take time and are rarely (or i should say, were rarely - because very few production shops make high quality metal frames any more atmo...) seen when high numbers are produced. but for a working effbuilder, the pinning should be thought of as a safety net, or a value-added q/c step, that allows him to take a concept, design it using precise steps, and then braze it all "on space", all the while knowing from repetition which way the metal pushes and pulls. the pins (and tacks) don't replace the very important steps that precede their use.

ps i use a #51 drill bit and common finishing nails that i buy by weight, and then taper/burnish the ends so that when i drive them in hard, they set up in the hole and hold a joint to my satisfaction. also - the fork fixture is there in my flickr sets, about 8 pages back.