Re: [CR]RE: Shimano 600 EX headsets & Bidding on Ebay

(Example: Racing:Wayne Stetina)

Date: Sat, 08 Mar 2008 11:36:34 -0600
Organization: The Crimson Permanent Assurance
Subject: Re: [CR]RE: Shimano 600 EX headsets & Bidding on Ebay
References: <>
In-Reply-To: <>
From: "John Thompson" <>

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 (
Appleton WI USA