As a machinist ,it piqued my curiosity. I've worked with BSP threads before,
but only to replace them with BSP threads.
According to The Machinists' Handbook, BSP threads differ in pitch, and
minor diameter from NPT threads.
pipe size BSP NPT
1/8 28tpi 27tpi
1/4 18tpi 19tpi
3/8 18tpi 19tpi
1/2 14tpi 14tpi minor diameters
differ by .0186"(BSP being larger)
3/4 14tpi 11tpi
1" 11.5tpi 11tpi
All this goes to show that the small differences in thread per inch counts
are just enough to allow a plug to start and feel like it "might be right"
and thus lead the uninitiated or ham-fisted to cross thread a similar yet
incorrect plug in place.
If you want to know if your plug is BSP or NPT, take it to a nearby Hardware
store, or your friendly local machinist, and have them use a thread pitch
gage on it
to find it's pitch.
Mark Haynes
'62 HAN6 RMVR
> -----Original Message-----
> From: Michael Dietsche [SMTP:mdietsche@yahoo.com]
> Sent: Monday, March 15, 1999 2:12 PM
> To: Lancer7676@aol.com; racer45@bellsouth.net
> Cc: spridgets@autox.team.net
> Subject: Yep -- Threads again.....Was Bulbs
>
>
>
> My whole point in asking the thread type for Midgets was to avoid this
> kind of nonsense by using the right plug to begin with. I have some
> reason to suspect that the drain threads might be British plumbing
> standard, and if so then screwing in something from the local American
> hardware store might cause the above-mentioned nightmare. I don't
> know that for sure, but I'd like to know before experimenting on my
> pan, tranny case or axle -- that's why I asked the question. If
> someone can tell me that American threads are compatible here I'll
> happily use American drain plugs! Till then I remain
> suspicious......just because you can wrestle a part in place doesn't
> mean everything's ok.
>
> Michael
>
> ---Lancer7676@aol.com wrote:
> >
> > In a message dated 3/15/99 12:26:46 PM EST, mdietsche@yahoo.com
> writes:
> >
> > << anyone who has ever stripped the threads
> > on an oil pan will agree with me. >>
> >
> > Michael--
> >
> > There is some sort of insert you can buy that screws into stripped
> oil pan
> > threads--it has its own plug/bolt for draining the oil. I can't
> remember
> > where I saw it--coulda been JC Whitney or perhaps someplace like
> NAPA or
> > Advance. I am thinking it was Whitney.
> >
> > ---David
> >
>
> ==
>
> Michael B. Dietsche, P.E.
|