Facing and Chasing
What it is, history, and why it’s not part of our regular practice, but we’ll do it if you order them for $30 each.
“Facing” is squaring up the ends of the head tube bottom bracket shell, using professional shop-grade hand tools and cutting oil. Faced head tubes and bottom bracket shells are parallel and perpendicular to the other axis of the frame. Don’t be thrown off by “other axis.”
“Chasing” is cleaning up the threads of paint or grit—wherever there are threads, like on the rear derailer tab and the bottle bosses. You do that with hand tools called taps, or you can just run a bolt through there. On new frames, it’s usually paint, not grit. If it’s grit, you blow it out with compressed air. You don’t run a tap thru it and hope it gets pulverized.
When you spray paint a frame, that paint can go anywhere, it can fit into gaps and crevices, and sometimes it can get in the threads. It depends entirely on how well the painter blocks the spray. On our bikes, it’s 98 to 100 percent blockage, just with an ultra-low tech cardboard tube stuck in there.
F and C sound like sound professional practices, but sometimes they don’t make sense. In the old days of steel frames—pre-1980s, when head lugs and bottom bracket shells were stamped out of flat sheets, then rolled into three-dimension fittings and welded, the ready-to-braze piece would be cockadoodle, just slightly. The “bike shop thinking” back then was: No biggie on cheap bikes, but on Colnago and Masi frames, we should fix that.
Investment castings are really precise. The tube-ends are square from the start. You can still face them, but it’s taking off paint that, in the case of bottom bracket shells, you shouldn’t remove. With cartridge bottom brackets nothing butts up against them, so a faced bb shell would just expose raw metal to the elements, and over time it would rust. RUST is not a biggie on a thick bottom bracket shell, but there is zero benefit to doing it, and the paint is nice coverage.
Up on the head tube, the investment cast lugs are (as already said) precise and square. When we install cups we look for gaps, and we see ‘em we’ll face it. Otherwise, no need. You can say “yes maybe, but on principle…”—but that’s not a good enough reason. We’ll do it for $30, but we have NEVER had a problem from not doing it. The bearings run smooth, headsets seem to last 15, 20 years, so we recommend not worrying.