Help: 2 questions on NPT threads!

[chickentendah]

Are male NPT threads supposed to screw ALL THE WAY INTO a female NPT thread?

Are you supposed to use teflon tape with NPT threads? Why?

Any help would be greatly appreciated, since I'm trying to figure out why my gauge senders are not screwing into what they're supposed to screw in.

[NoStickers]

NPT is tapered so it won't screw all the way in, just kinda wedges itself and ya I'd use teflon of course to seal the threads.

[chickentendah]

NPT is tapered so it won't screw all the way in, just kinda wedges itself and ya I'd use teflon of course to seal the threads.

ahhhhhh, that explains a lot of things.......for a while i thought I had the wrong senders etc..........thanks NoStickers

while we're at it, lemme pose the same two questions for japanese PT threads:

Are male PT threads supposed to screw all the way into female PT threads?Are you supposed to use teflon tape with PT threads? Why?