[mannykannot]

What do you think of the advice that it is acceptable to use a tapered male thread in a straight female one? My guess is that if you do that, you have at best one turn of the thread helix holding them together and providing a seal (and perhaps you would be trusting in nothing more than the tape jammed between the threads if you used ten turns of it!)

[johnwalkr]

I don’t think it’s acceptable. Maybe works in pinch to get through a weekend but I would always replace it with a proper fitting. Plus if you damage the female threads or o-ring seat, you’ve made a much worse problem for yourself.

[ethbr0]

It's probably a commentary on the idea that the tapered male diameter is its max diameter(?), versus straight is throughout.

Consequently, a tapered male will fully screw into a straight female, albeit with gaps between the threads at the deep end of the socket.

Whereas a straight male will at most only screw the first few threads into a tapered female, leaving most of the male hanging out.

[johnwalkr]

Tapered pipe threads are actually much larger than you’d expect given the nominal diameter. 1/4 inch tapered pipe threads have a maximum outer diameter of more than 1/2 inch and 18 threads per inch. They will sort of work with a 1/4 inch straight thread but not by fully screwing in.

[lazide]

It’s asking to rip the threads out of the fitting (and have done so when trying). One way you’ll get some seal first, the other you won’t.