Thanks to Mark I figured it out. 8mm X 1.25mm is right.
I guess some Williams engineer decided the metric coarse thread had an advantage over the Stronglight/Campagnolo selected 8mm X 1.0mm. The rest is history.
Joe Bender-Zanoni
Great Notch, NJ
> Hi Joe,
>
> Re: AB-77 bolts:
>
> Just measured mine; unfortunately they're both in somewhat rough shape.
Though they thread in to the axle smoothly enough, the threads look like
they are deformed from overtightening. At .310 diameter, could be nominal
5/16" (.3125) or 8mm (.3150). I have inch and metric thread pitch gauges
and the 20 tpi gauge looked to be a noticeably better fit than the 1.25 mm,
though neither was perfect.
>
> If I was a betting man I'd put money on 5/16" x 20 tpi.
>
> Interestingly, the bolt heads are right on 15 mm, which isn't close to any
normal inch-size wrench I know of. I think the heads were probably made to
fit Campy and other tools a bike mechanic was likely to have.
>
> -Mark