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Neck Surgery


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?