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Valve core thread dimensions
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 |
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Valve core thread dimensions
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. I've emailed a company that makes extenders and asked if they'll reveal the secret dimension. A real mechanic would simply measure the threads with a gauge, but I've seen enough loosely-fitting extenders to wonder just how easy the measuring of such small threads is. Most of the extenders that I've seen worked much better with a couple of twists of teflon plumber's tape around the threads to seal the connection. You'd also have to cut the very end off a Presta valve to get the little knurled nut off, slip the valve through the extender, and put the screw back on. A new Tufo clincher-tubular is probably a lot less fuss. Cheers, Carl Fogel |
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Valve core thread dimensions
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Valve core thread dimensions
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Valve core thread dimensions
On Mon, 25 Sep 2006 17:58:54 GMT, Werehatrack
wrote: On Sat, 23 Sep 2006 10:51:51 GMT, wrote: Presta main - m6-0.75 Presta cap - m5-1.0 Both of those are remarkably uncommon sizes. Good luck finding a tap or die in those thread and diameter combinations outside of a specialty tool supplier. Got both of 'em in a cheap carbon-steel set at the local discount tool emporium. You must live in a tool-parched land. |
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Valve core thread dimensions
On Mon, 25 Sep 2006 18:05:51 GMT, wrote:
On Mon, 25 Sep 2006 17:58:54 GMT, Werehatrack wrote: On Sat, 23 Sep 2006 10:51:51 GMT, wrote: Presta main - m6-0.75 Presta cap - m5-1.0 Both of those are remarkably uncommon sizes. Good luck finding a tap or die in those thread and diameter combinations outside of a specialty tool supplier. Got both of 'em in a cheap carbon-steel set at the local discount tool emporium. You must live in a tool-parched land. Dear J & W, Hmmm . . . I'd split the difference between your positions. Lots of cheap tap and die sets in the U.S. include m6 x 0.75, but none seem to include m5 x 1.0. Here's an $8 Harbor Freight set with m6 x 0.75, probably good enough for the metal in valve stems: http://www.harborfreight.com/cpi/cta...emnumber=39384 Sears doesn't even bother to list details in their tap and die sets beyond "60 pieces" and seems to have nothing as m5 x 1.0. This place offers a 5 mm x 1.00 die for $8.50: http://www.victornet.com/cgi-bin/vic...,90 5,606,607 Cheers, Carl Fogel |
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Valve core thread dimensions
In article ,
Werehatrack wrote: On Sat, 23 Sep 2006 10:51:51 GMT, wrote: Presta main - m6-0.75 Presta cap - m5-1.0 Both of those are remarkably uncommon sizes. Good luck finding a tap or die in those thread and diameter combinations outside of a specialty tool supplier. I don't believe these threads are correct. The presta valves I've measured have inch-based thread pitches - 32 and 24 tpi respectively. But in this case, I think the OP was looking for neither of these, but rather the internal thread in a removable-core valve stem. That, I haven't measured. However, I think it's a moot point: there's more going on inside the valve stem than just that thread - the seating area that the valve core seals against needs to be shaped appropriately too, and it seems like more trouble than its worth to try to reproduce it all. Were it me, I'd probably just slather some epoxy in the stem where the crack is, and permanently glue an extension in place, letting the epoxy seal whatever crack is there. -Luns |
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Valve core thread dimensions
On Tue, 26 Sep 2006 00:31:05 +0000 (UTC),
(Luns Tee) wrote: In article , Werehatrack wrote: On Sat, 23 Sep 2006 10:51:51 GMT, wrote: Presta main - m6-0.75 Presta cap - m5-1.0 Both of those are remarkably uncommon sizes. Good luck finding a tap or die in those thread and diameter combinations outside of a specialty tool supplier. I don't believe these threads are correct. The presta valves I've measured have inch-based thread pitches - 32 and 24 tpi respectively. But in this case, I think the OP was looking for neither of these, but rather the internal thread in a removable-core valve stem. That, I haven't measured. However, I think it's a moot point: there's more going on inside the valve stem than just that thread - the seating area that the valve core seals against needs to be shaped appropriately too, and it seems like more trouble than its worth to try to reproduce it all. Were it me, I'd probably just slather some epoxy in the stem where the crack is, and permanently glue an extension in place, letting the epoxy seal whatever crack is there. I rechecked the dimensions; 6x.75 and 5x1.0 are correct for Presta externals on all of mine. 1.0 is very close to 24tpi, and .75 is close to 32tpi, but the thread guage for the metrics was clearly a better fit than the US guage. While mixed metric/inch thread choices have been seen elsewhere on bikes (notably on some Raleigh bits as I recall), the Presta stem apparently isn't one of them. -- Typoes are a feature, not a bug. Some gardening required to reply via email. Words processed in a facility that contains nuts. |
#10
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Valve core thread dimensions
In article ,
Luns Tee wrote: Presta main - m6-0.75 Presta cap - m5-1.0 I don't believe these threads are correct. The presta valves I've measured have inch-based thread pitches - 32 and 24 tpi respectively. I don't believe I should continue to trust my memory. I remember being surprised with what the threads turned out to be, and it involving inch pitches, but extrapolated that too far. The main shaft threads are indeed metric, although it's a 0.8mm pitch rather than 0.75. My surprise was with the cap threads, which on looking at them again, still seem to be 24tpi to me. With only three thread crests at most, it's very hard to discern a difference between 24tpi and 25.4tpi, but this just highlights how unimportant the matter is. Trying to determine the gauge by looking at thread crests is misleading, as the final turns are truncated, making the apparant crests closer spaced than the actual pitch. Comparing against a 1.0mm reference, the crests appear to match, and the threads seem to fit, but on the valves I checked, contact is on the flanks of the outermost turns of thread, with the middle turn making no contact at all, and crests not reaching the thread root. The orientation of the contact indicates the thread is a coarser pitch than 1.0mm. Putting a 24tpi gauge against the cap threads, the gauge's crests land consistently in the valve's thread roots. -Luns |
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