Re: [CR] French thread crankset

(Example: Racing:Beryl Burton)

Date: Mon, 05 Apr 2010 12:47:41 -0700
From: "verktyg" <verktyg@aol.com>
To: Tom Hayes <hayesbikes@gmail.com>, Classicrendezvous@bikelist.org
References: <p2n779093151004051222mfa6bdf15z6d64c04f62b4f50e@mail.gmail.com>
In-Reply-To:
Subject: Re: [CR] French thread crankset


Tom,

This has probably been covered many time in the archives, but here gos,

14mm = .5512" 9/16 = .5625"

That's .0113" diameter difference, rounded off to .011".

20 TPI (threads per inch) pitch = .050" = 1.27mm 1.25mm = .0492mm

The thread pitches are about the same.

Taping metric threaded crank arms oversize is pretty easy with good sharp taps with a decent lead on them to act as a reamer. Some pedal taps came with a built in reamer to remove th ~.005" per side.

The biggest issue besides tap quality is using an effective tapping compound that will prevent galling on the tap.

Chas. Colerich Oakland, CA USA

Tom Hayes wrote:
> I have a Stronglight 93 crankset marked 14 x 125. When I got it, it
> had*clearly marked 9/16 x 20 Campagnolo pedals. They tighten onto the
> crank
> * smoothly, evenly, and tightly. The pedal holes do not appear to have been
> changed--retapped; or if they were, no indication of such tapping is in
> evidence.
>
> I am trying to play possibilities on this: the crank arms are mislabeled,
> the pedals are mislabeled (though I tried others on this crank), excellent
> job of retapping, or my bad eyesight (I am leaning toward this). Any
> experience from other members?
>
> Thank you.
>
> Cheers.
>
> Tom Hayes
> Chagrin Falls, Ohio USA