[CR] Fender Eyelets: British bike threading is NOT Whitworth!!!!

Example: Framebuilders:Dario Pegoretti

Date: Thu, 12 Feb 2009 22:40:09 -0600
To: CR discussion list <classicrendezvous@bikelist.org>
From: Mark Stonich <mark@bikesmithdesign.com>
In-Reply-To: <5B8B9C200C104480B21561AB92D16E5A@KenPC>
References: <COL113-W15548C5AB26EFC43C1BDD1F5BB0@phx.gbl>
Subject: [CR] Fender Eyelets: British bike threading is NOT Whitworth!!!!

At 2/12/2009 04:26 AM -0500, Ken Sanford wrote:
>you don't identify the nationality of the bike. If it is British
>from say approximately 1965 or earlier,then the threading is likely
>Whitworth. If some other nationality then I doesn't know.

British bike threading is NOT Whitworth!!!! (*)

This is a common misconception, because many 26 tpi BSC fasteners had the same nut and bolt hex sizes as Whitworth threaded fasteners so Whitworth tools fit.

26tpi is BSC British Standard Cycle. In most sizes this is a rather fine thread, intended to avoid loosening from vibration on cycles, motorized or not. Whitworth is a much coarser thread, same pitch as UNC in most sizes but with 55 degree threads vs, the 60 degree threads of the BSC and UNC.

I wonder if the 10mm x 26tpi Campagnolo axle threading had something to do with buying British lathes, surplus from the cycling industry, that would only do 26tpi.

Another possibility is that older eyelet threads are the coarser, pre-ISO 5mm x 0.9mm. Mostly on French bikes but IRRC the Campagnolo 1060 dropouts on my Jack Taylor are 5mm x 0.9mm. Screws from old French derailleurs will sometimes work.

(*) There are no absolutes when talking about the British cycle industry so I imagine somewhere, somewhen, something with Whitworth threading was used, but I've never heard or seen of it happening.

Mark Stonich;
     BikeSmith Design & Fabrication
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