"DAKSY" <rsmith13@nycap.rr.com> wrote:
: Hey, Mr. Steiger...
: <snip> : What's the thread size for the schrader valves?
: Its a weird one. .305-32. (.305" diameter, 32 threads per inch)<snip>
: Actually, it's not. I'd say it meets the criteria for a 5/16 - 32UNEF - 2A
: thread.
Bob, thanks for taking the time to check into that! I hate to be
argumentative with ya, :-) but I am sure that the thread size is .305-32,
because the Tire and Rim Association says so, and that thread size is
spec'd out all over the place for tire valve stems. According to the
TRA, its a 7.7mm diameter (0.303149606") with a minor diameter of 6.9mm
(0.271653543"), however they list the thread as .305-32 (or 7.7-32).
: The max specified size of the majot thread diameter is .3115"
: The tolerance on the major thread diameter is -.0060"
: Therefore the min. minor thd. dia. is .3055"
Was "minor" a typo and you meant to say that the min. major
diamter is .3055? I hope so, cause otherwise you lost me. :-)
(I'm just barely keeping my head above water on this stuff as it is!) :-)
: If your measuring skill & equipment can accurately read out to "tenths",
: it's undersize by 1/20th the thickness of a sheet of Kleenex (kinda small),
: which would be negated by a thread sealing compound, IMHO...
It sounds like a 5/16-32 might be close enough to cram a bolt of that
spec into a .305-32 thread, but I'm not sure if it would work the other
way around (trying to tap female threads to fit onto a standard male
.305-32 fitting). The problem is exacerbated by the fact that I don't
know the tolerances for the Schrader threads, but since they spec it
out at .303 OD (if you go by the metric), and the threads I have measured
have been around .302, the minimum major diameter of .3055 on the 5/16-32
is already starting out around 2.5 thousandths too big, which is a pretty
small difference, but on the other hand, 32 TPI is an awfully shallow
thread to begin with so I don't know how much it can be pushed before its
just going to slip or strip.
I'm tempted to just build the darn things myself, if I can obtain
the proper tap. I haven't had much luck with .305-32, but it might
be worthwhile to grab a 5/16-32 along with some hex brass stock and
chuck it up in the lathe and see what happens. It might be possible
to drill slightly smaller than the recommended drill size for 5/16,
maybe go with a drill like 19/64 and see if that 5/16 tap won't
ram through there. Or maybe I'll drop by the local machine shop
and see how much they might want to crank these out...
--
-Jon-
.- Jon Steiger --- jon@dakota-truck.net or jon@jonsteiger.com -.
| 67 Dodge Coronet, 70 Plymouth Barracuda, 76 Peugeot TSA |
| 78 Dodge B100, 90 Dodge Dakota Convertible, 92 Dodge Ram 4x4 |
| 96 Dodge Dakota, 96 Suzuki Intruder 1400, 96 Kolb FireFly |
| 99 Jeep Cherokee 4x4, 2001 Dodge Ram 3500 CTD |
`--------------------------------- http://www.jonsteiger.com --'
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