Re: Stem tightening, was Re: [CR]The Zen of 7 mm Hex Key stems

(Example: Framebuilding:Brazing Technique)

From: "Galen" <>
To: "Fred Rafael Rednor" <>, <>
References: <>
Subject: Re: Stem tightening, was Re: [CR]The Zen of 7 mm Hex Key stems
Date: Wed, 4 Jan 2006 06:00:34 -0600


Unlike some metric sizes, in which there is an SAE size that is "close enough" there is nothing really close to 7 mm in the SAE box. 1/4 inch is about 6.3 mm, and using a tempered 1/4 inch allen key is likely to damage the faces on the bolts. A 5/16 is too large to fit. I'm not aware of a 9/32 inch allen, but they may have been used for specialty applications. Other than the guys with all the older British bikes, who need Whitworth sized wrenches, if you own a European or Japanese bike, get a decent set of metric tools. Your fasteners will last longer and look better!

Galen Poole
Jackson, MS

----- Original Message -----
From: Fred Rafael Rednor
Sent: Tuesday, January 03, 2006 11:23 PM
Subject: Re: Stem tightening, was Re: [CR]The Zen of 7 mm Hex Key stems

> > Does the 7mm correlate to an SAE size?
> Actually... no!
> Amazingly, there isn't really _that_ great a size difference
> between 1/4 inch and 7mm, yet we see this diversity. This
> should amuse you:
> I just went down to the dungeon and examined a bunch of old
> stems (but new enough to use hex keys for the binder bolt) and
> here are some examples of what I found:
> My oldest Cinelli stem - 7mm
> TTT Gran Prix - 7mm
> TTT Record - 7mm
> Pivo - 7mm for both quill and handlebar binder
> Balleri, "sample #1" - 7mm for quill and 5mm (!)
> for the handlebar binder
> Balleri, "sample #2" - 6mm
> Everything else, be they French, Italian or Japanese, uses 6mm.
> That includes stems from CTA, Cinelli, TTT, Nitto, SR and a
> few unmarked pieces.
> So what does this prove? I don't know... but it might
> answer Peter Kohler's question regarding why MAFAC did not
> include a 7mm key in their little tool kit. That is, even the
> bicycle manufacturers might not have known what size key was
> appropriate on any particular day of the week. But isn't that
> one of the things what makes these bikes so interesting?
> Cheers,
> Fred Rednor - Arlington, Virginia (USA)
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