[modeleng] Re: coarse threads

They did it so folks couldn't easily connect gas to water etc.

Cheers Jeff Dayman
----- Original Message ----- 
From: "Jesse Livingston" <fernj1@xxxxxxxxxxxxx>
To: <modeleng@xxxxxxxxxxxxx>
Sent: Saturday, January 27, 2007 6:23 AM
Subject: [modeleng] Re: coarse threads


> Here, 27tpi is used for, or used to be used for brass pipe gas threads.
>  Our pipe threads are 28 , 19, 14, 11 tpi according to size.
>  Alan Stepney
>
>
> Alan et al,
>
> Wonder why they went from 27 tpi to 28 and why did some idiot come up with
> the 27 thread idea in the first place?  I have cut 27 tpi on my Atlas
lathe
> once upon a time, but I had to do it the same sneaky way I do when I cut
> metric threads on Imperial geared lathes.  I have no idea why I needed 27
> tpi since my lathe has no taper attachment and it would have been a
tapered
> thread or so I would think.  I have a taper attachment on the 14" Rockwell
> lathe out in the back shop and have used it to make oversized pipe plugs
for
> a friend's steam traction engine.  One or two of the 2-1/2" pipe cleanout
> plugs in his firebox had been in and out so much that the threads had
> stretched/worn enough the regular pipe plug was in danger of screwing all
> the way into the water leg.  An extra long plug took care of that and
boiler
> passed the Kentucky boiler inspector hydro test OK.
>
> Red Neck Jesse in Tennessee
>
>
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