William Strang wrote:
> The special scalloped headset wrenches may be
> desirable to fit the 600 EX headsets, because while a
> regular 32mm HS wrench fits, using one tends to
> ovalize the top nut, presumably because the cutouts
> weaken the nut.
No; the scallops were put on because of concern that the aluminum nut would be easily damaged by a standard flat jaw wrench. Using the special wrench protects the nut by increasing the contact area between the wrench and nut. With a flat wrench on a flat nut, only the corners of the nut take the load from the wrench; these are the same areas that a flat wrench contacts when using one on the scalloped nut. Removing the material to produce the scallop does not significantly weaken the nut, but does allow a scalloped wrench better contact.
FWIW, Snap-On's "flank drive" wrenches are designed on a similar principle.
--
-John Thompson (john@os2.dhs.org)
Appleton WI USA