This week our Belgian friend Chris brought us his girlfriends
bike, which had an upper neck bearing cup that was completly loose
in the frame. This bike used to have a sidecar, so that might
have had something to do with it, in any case the hole in the
neckcasting was oval shaped and the bearing cup could move back
and forth about a mm. He asked if we could fix that without disassembling
the whole bike.
Aad built a jig with 2 big ball bearings that could be used
with a boring bar to machine the hole oversized so a ring can
be pressed in and the (new) bearing cup would fit perfectly again.
The 3 big bolts on the middle part allow the jig to be very
precisely positioned, and Aad ground his own cutting tool from
an old end mill.
The newly made cutting tool fits in a hole in the boring bar,
and is held in place by 2 setscrews. It took several hours to
make the jig, but the actual machining took only 5 minutes, worked
perfectly! Anyone else have wornout neck?