A Cycling & bikes forum. CycleBanter.com

Go Back   Home » CycleBanter.com forum » rec.bicycles » Techniques
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

Valve core thread dimensions



 
 
Thread Tools Display Modes
  #11  
Old September 26th 06, 11:59 AM posted to rec.bicycles.tech
[email protected]
external usenet poster
 
Posts: 883
Default Valve core thread dimensions

On Tue, 26 Sep 2006 07:35:53 GMT, Werehatrack
wrote:

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.


This is the world of cycles, remember; the posibility of an
inch-threaded presta valve existing cannot be discounted - but mine
were all metric (I used a loupe to check them). Someday I'll figure
out the thread size for the jam-nut.
Ads
  #12  
Old September 27th 06, 09:01 PM posted to rec.bicycles.tech
Luns Tee
external usenet poster
 
Posts: 92
Default 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
  #13  
Old September 27th 06, 09:13 PM posted to rec.bicycles.tech
[email protected]
external usenet poster
 
Posts: 7,934
Default Valve core thread dimensions

On Wed, 27 Sep 2006 20:01:16 +0000 (UTC),
(Luns Tee) wrote:

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


Dear Luns,

Thanks--you and the others are making me feel better about not trying
to measure those tiny threads with my pathetic mechanical skills.

Here's what happened when I emailed a company and asked about the
threads on their Presta extender:

***

From:
To:
Sent: Friday, September 22, 2006 7:45 PM
Subject: Presta thread pitch and size?

Hello,

Can you tell me what the thread pitch and size is for the smaller
Presta valve cap section, the end part of the valve that your Presta
extender fits?

Thanks,

Carl Fogel

***

From: "Info @ Wheels Mfg"
To:
Subject: Presta thread pitch and size?
Date: Monday, September 25, 2006 6:57:58 AM

Not off the top of my head Carl. You could measure one!

Dave in sales

***

I note with alarm that the ubiquitous Daves who swarm on RBT are now
spreading even into the sales departments.

Cheers,

Carl Fogel
  #14  
Old January 4th 18, 01:26 AM posted to rec.bicycles.tech
[email protected]
external usenet poster
 
Posts: 1
Default Valve core thread dimensions

Schrader valve

External thread: 5/16x32 fine thread

Internal thread: 0.209 in OD x 36 TPI

Presta valve

The valve threads for Presta valves follow the ISO 4570 standard.[4][5]*The external threads at the tip of both "threaded" and "unthreaded" Presta valves are 5V2, which measures out to 5.2×1.058*mm.[6]*The external threads on the main body of "threaded" Presta valves are 6V1, which measures 6×0.80
  #15  
Old January 4th 18, 01:47 AM posted to rec.bicycles.tech
Earls61
external usenet poster
 
Posts: 21
Default Valve core thread dimensions

Whoa! Blast from the past! Whatever happened to Carl Fogel?
  #16  
Old January 4th 18, 03:43 AM posted to rec.bicycles.tech
Frank Krygowski[_4_]
external usenet poster
 
Posts: 6,415
Default Valve core thread dimensions

On 1/3/2018 7:47 PM, Earls61 wrote:
Whoa! Blast from the past! Whatever happened to Carl Fogel?


I don't know, but I miss him.


--
- Frank Krygowski
  #17  
Old January 4th 18, 07:40 PM posted to rec.bicycles.tech
[email protected]
external usenet poster
 
Posts: 6,374
Default Valve core thread dimensions

http://www.cyclingforums.com/threads...-fogel.298931/
 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
GOOD for Your CORE ? trailguy Unicycling 23 March 10th 07 09:11 AM
schraeder valve thread? A Muzi Techniques 5 March 21st 04 11:15 PM
Tyre suddenly leaks air at valve. HELP! gkmac Unicycling 5 December 16th 03 11:20 PM
"Liquid Drive" bike prototype at auction Chalo Techniques 87 December 3rd 03 06:41 AM
Valve Extender Woes Justin F. Knotzke Techniques 8 August 19th 03 03:19 PM


All times are GMT +1. The time now is 11:54 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.
Copyright 2004-2018 CycleBanter.com.
The comments are property of their posters.