Originally Posted by
maddog34
FBinNY hasn't posted to the forums since March 2nd of this year...
i hope he is ok.
if you want to mount a plastic guide to the underside of the BB plus drill a drain hole... remember to use a stainless steel screw that is just barely long enough., or it will possibly interfere with the bottom bracket assembly..., and lightly chamfer the drain hole to reduce the chance of cracking...
the usual thread is a 5 x.8mm... Tap drill size is 4.2mm, or .165", A number 19 drill is .166"... it'll work fine.
the groove Francis was referring to is a gutter filed into the plastic guide to allow the water to drain out to the rear... from location of drain hole, to the rear edge of the plastic guide.
That is an unusually long time for FBinNY, ditto the well-wishing.
Chamfer both sides of the drilled hole I suppose? And thanks for the detailed advice! Should be easy for me, now.
Originally Posted by
grumpus
A lot of vintage bikes were intended to use a clamp-on guide like these (the Zeus and Campy ones):
https://bikerecyclery.com/cable-guides-stops-clips/
which would be a nice period touch if your chainstay cable stop is on top.
They fell out of favour when indexed gears became the norm, replaced by the under-bracket plastic guides.
Personally I don't get why things changed to under the bottom bracket. Cables are less clean, and I feel like the routing, especially the front derailleur, is better when ran above the bottom bracket. The frame is in question has the chainstay cable stop below, rather than above, but just has some grooves in the bottom bracket rather than a plastic guide. Hence the drilling!