Making NPT Threads

[Philjoe5]

I'm looking at the plans for my latest project and it calls for making a packing nut with 1/8" NPT outside threads. I'm planning to get a 1/8" NPT Die to make these, but do I taper the stock first or cut threads as I would for standard machine screws? Thanks for any help,

Cheers,
Phil

 

[tattoomike68]

I fake taper pipe threads by turning the tool upside down and threading away from the chuck and running backwards while slowly plunging the crossfeed in. I know that sounds crazy.

On big yapered pipe threads I would cut a little taper to start with.

It takes a little practice but work very well.

 

[rake60]

Joe if you are making the packing nut of brass you can usually
get away with turning the stock to the standard nominal O.D.
of .405" and and the die will go with a little effort.
I turn that fit in the lathe then run the die onto it using the flat
side of the tool post to keep it square as well as adding a little
inward pressure to keep the threads from pulling.
I turn the die handle so it's making contact with a thin rubber
pad placed on the ways of the lathe and turn the chuck by hand
to cut the threads.

THEN I drill and ream the center hole, and part it off.
I use hex stock if I can find it. If not, I mill the flats.

Just my way of doing it.

Rick

 

[Philjoe5]

Thanks for the help Rick and TattooMike. Rick, that's exactly how I cut screw threads but have never done NPT so didn't know if something special was needed. TattooMike, someday when I have a lot more gray hairs than I do now, I'll learn to cut some decent threads on the lathe. For now I've gotta use the dies and diestock. I even made a nice 1" tailstock dieholder that gives me nice true threads ;D.

Cheers,
Phil