Tom,
As already mentioned, there are other tools from Sugino and Shimano that have a protrusion which centers the tool in the chainring nut. You can put this in place under the crank on your bench and apply downward pressure with your allen wrench while trying to loosen the bolt.
I'd try all the non-destructive options that you can find, but if all else fails, you can probably drill off the bolt's head, they're not very thick. Put a countersink or sufficiently large drill bit into your drill and drill down into the face of the bolt until the bolt's head is cut loose from the hollow threaded shaft. If the bolt is spinning you may be able to hold it with the aforementioned tool or "jam" it by gently pulling the chain rings apart. Don't use too much force or you'll bend the mounting tabs.
This is a good example of what happens to threaded fasteners that are assembled without grease or anti-seize compound. Factory assemblies are often not greased. I take new cranks apart to grease these bolts.
Ed.
> I have a chainring bolt, campagnolo, that I have so far be unable to get
> off the crank. It is holding (the remaining one) two NR chainrings
mounted
> to a GS crankarm, if that makes any difference.
>
> I have used the appropriate Campagnolo took with the little prongs; one of
> the backside slots is now slighly mangled. The bolt and fastner keeps
> turning together, and I cannot find a tool, or any other device--already
> tried a large screwdriver-- that will fit the slots that I can hold
> sufficently tight to loosen the screw with the hex wrench. I've tried
> needle nose pliers holding the backside, used enough liquid wrench. I've
> exhausted my limited understanding of tools and bankrupted my equally
> limited imagination for devising something that would work.
>
> Any help out there.
>
> Thanks.
>
> Tom
> Tom Hayes
> 18585 Munn Road
> Chagrin Falls, Ohio 44023
> hayes@jcu.edu