[CR]Tapping out French threading...Caution

(Example: Framebuilding:Tubing)

Date: Sun, 11 May 2003 15:06:16 -0400
From: "HM & SS Sachs" <sachs@erols.com>
To: jerrymoos@sbcglobal.net, classicrendezvous@bikelist.org
Subject: [CR]Tapping out French threading...Caution

Date: Sun, 11 May 2003 08:51:41 -0500 From: "jerrymoos" Jerry Moos about said it all:

David, French thread was 14 mm x 1.25 mm, English is 9/16 inch x 20 TPI. That means English pedals had a thread diameter of 14.28 mm versus 14.0 mm for French. These are nominal. If you followed the thread on TA pedals a couple of week ago, you know the actual diameters were usually 0.1 mm to .02 mm smaller. 20 TPI works out to a 1.27 mm pitch, so the pitch was nearly identical. A lot of old French cranks are marked 14 x 125 on the back of the arms.

What you observe is typical of English pedals in French cranks, i.e. they go in OK for a couple of turns, then tighten up. You can buy taps for tapping out French threaded cranks to English thread. Several shop owners on the list sell these. Since the difference is only 0.28 mm, tapping is fairly easy and was commonly done back when French cranks were more common. <snip>

I'd just add that the commonly available and relatively inexpensive tap sets are not always appropriate for tapping out steel cranks. I beat up one pair pretty badly trying to adapt a set of steel cranks for a Peugeot for my mother (how appropriate to remember on Mother's Day!).

harvey "what was I thinking, anyhow?" sachs