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Old 03-16-2010, 09:39 AM
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Originally Posted by smithkustoms
BONUS QUESTION: My compressor has a 80 gallon tank but only has a 3/8" outlet. The 3/8" threaded outlet is on a large (3-4") screw in plug like most compressors have. Can I drill and tap the 3/8" hole in the pulg for a larger 1/2" or 3/4" outlet?
If what you now have is actually 3/8 NPT, that IS large. If you're not familiar w/the NPT sizing (and skip this if you are), it's different than 'regular' threads like NC and NF.

What most guys will look at and call a 1/4" pipe thread is actually a 1/8 NPT. Same thing all the way up- the NPT size is numerically smaller than the size of the tap would lead you to believe.

That said, if you need to go larger than 3/8 NPT, the next up is 1/2 NPT. It's big. 3/4 NPT is BIG!

Originally Posted by Marquita
In theory you could drill it, get a tap in, but have the tap fly across the room when you first use it. That would scare me slightly, but I'm particularly bad at that kind of thing. My main concern would be how to do it AND withstand whatever pressure is in the tank on an ongoing basis without anything breaking or leaking.
I'm puzzled about the highlighted comment above.

What I believe smithkustoms is suggesting, is to drill out and tap for a larger diameter outlet. The hole would be drilled w/the proper bit for the NPT tap to be used to cut the threads, then the larger diameter pipe fitting would be screwed into the new hole. There should be zero reason to "have the tap fly across the room when you first use it".

Maybe you're confusing "tap" for a type of fitting, as opposed to the tool that cuts threads?
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