SpudFiles

To seal pipe threads, especially steel, I have to put it in a vice and then use a huge pipe wrench to really apply force until it finally seals. The thing is, I'm making a piston valve gun out of steel pipe, how can I access the piston and at the same time have that joint seal completely

Thread tape, (Teflon Tape).

Are you using Teflon Tape? If you are, are you using enough? [youtube][/youtube]

That should give you an idea as to how much

http://www.spudfiles.com/forums/viewtop ... tml#308638

Also found in this thread.

Pipe dope, I like the kind with teflon shreds in it. Works better than the tape which gets shredded by anything but brass and plastic fittings.

Apply the tape correctly and it doesn't get "shredded." I'm currently under the impression that the entire tape is teflon. It's called PTFE tape, and PTFE = polytetrafluoroethylene = teflon. Right?

Of course I'm using teflon tape, I thought that's only a lubricant though, and the pipe seals when you tighten it so much that it deforms the threads. I would think doing that time after time it would eventually lose it's seal?

Teflon tape is not only a lubricant. It does also lubricate, but it is intended to make the threads seal. Deforming the threads with two unlike metals like brass and steel may result in a permanent connection. Deforming the threads is not advisable. In addition, this may result. That was just using small hand tools, no vice.

Every time you unscrew the threads take off any excess that's hanging around and wasn't in the connection and apply new.

I was having trouble with teflon on galv steel pipes. Try the pink teflon that's intended for gas, it's a fair bit thicker and won't be chewed up by threads.

This product ALWAYS works and as I recall, it's rated to 3500 psi.

Loctite ® 55™ Pipe Sealing Cord

as long as you're applying the tape correctly, It will work on even large diameter steel fittings. I've never had one leak on me with properly applied pipe tape.