[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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