On Fri, 22 Sep 2006 22:39:11 -0600, wrote:

On Thu, 21 Sep 2006 15:31:46 GMT, "Mike Kennedy"
wrote:

Does anyone know what the thread dimensions are for a value core or the
threaded end of a valve extender? I have a split in the valve stem of a TUFO
tubular-clincher and I thought that I would cut the section off that has the
split, tap the section left and install an valve extender. Anyway I need to
know what threading to tap.

Thank you,

Mike Kennedy

Dear Mike,

There are actually two threads on a typical Presta valve stem.

One is the long base, which is wide and threaded for the jam nut that
is tightened down to the rim. "Smooth" Presta valves lack this
threading.

The other threaded section at the end of the valve. It's narrower than
the main body of the valve stem, has only about 3 threads, and is for
the valve cap (or a typical valve extender).

So your scheme may not work too easily, even if you know the thread
pitch and find a die. It sounds as if you want to cut off the end of
the valve stem with the crack, including the short, narrow part that
the valve cap or typical extender just barely threads onto.

If so, you'll have an uncracked stub left, but it will be too thick
for a typical valve extender and will have to be turned down somehow
before threading.

In any case, I'm damned if I can find either thread pitch on the
internet, even in the U.S. Patent Office site.

Shraeder external - 0.305-32 (5/16-32 UNEF will do)
Schraeder internal - 0.206-36 (#12-36 is a bit big)
Presta main - m6-0.75
Presta cap - m5-1.0