Ooops, I didn't looked close enough. Mark Bulgier corrected me and described it perfectly right:
"What you call a scratch is really a slot - the bolt is cut clear through. The allen-wrench or hex-key socket visible in the picture is the head of a small bolt that threads inside the larger bolt. The small bolt has a conical head that mates with a cone inside the larger bolt. When you tighten it, it makes the visible (in the picture) outer thread of the big bolt get larger by widening the slot - sort of like how a bar-end shifter is fixed inside the handlebar.
So the preferred mounting method is: Loosen the little bolt so the big bolt threads into the frame easily. Screw this big bolt in to the point where the derailleur is just able to swing on the frame, but tightly with some resistance. Then tighten the little bolt until the big bolt is held tight in the frame to maintain the adjustment."
That he is right can be seen at
http://home.t-online.de/
The bolt on the right hand side is one of an earlier Jubilee derailleur and is a simple bolt. BTW: They are not interchangeble because of the different diameter.
Dirk
-- Dirk Feeken Heidelberg Germany
-----Original Message----- Subject: RE: [CR]Huret Jubilee question - pics
Here you are:
http://home.t-online.de/
The plate is made of 2mm steel, the hole has a diameter of 10mm and is not threaded and rotates freely on the mounting bolt. The bolt has a tight fit in the threads of the drop out, because it must not be tightened completely otherwise the derailleur wouldn't rotate. The mounting bolt of late Jubilees has even "factory scratched" threads (the dark line across the threads) to hold the bolt in the drop out without an additional nut.
Dirk
--
Dirk Feeken
Heidelberg
Germany