So I have been trying to find a 3/4"-14 NPSM (Straight threads) Male to a 3/4" NPT (tapered threads) Female, adapter or nipple. It's like they don't exist, I can find a straight thread female to tapered male, but not the other way around. I really need this to use a scuba tank. It's like the scuba tank manufacturers know choose a thread size and count that no one can find. Does anyone have any insight or sources for one of these?

check a place that sells hydraulic fittings, hoses.

I would try Mcmaster-carr, then hydraulic shops, and then the welding/medical gas supplier/dealers.

check out part # 48773899 on page 4062 in the MSC catalog.
http://www1.mscdirect.com/CGI/NNPDFF?PMPAGE=4062&PARTPG=GSDRVSM&PMT4NO=59229080&PMITEM=62397302&PMCTLG=00&PMT4TP=*LTIP

I work in the scuba industry and do HP fill stations. What are you trying to do?

If you want PM me and I'll be happy to try and help you find the fittings if posible.

If you are trying to do what I think you are, you might be SOL with standard fittings. There are a few other options but I won't post them publicly.

I guess it all depends how bad you want to do this .

Have your local machine shop make you one.

I also can think of a way to do this but not in public:D

Could you find a fitting that works and drill/tap it for pipe threads?

Andy

Gee, my hydraulic shop gets me straight pipe fittings all the time.

Also, keep looking, there are multiple sources for fittings to convert breathing air tanks to standard pipe fittings, these are standard in the fire service so that SCBA tanks can be used for pneumatic purposes.

Might check the Scott website, that's where I found the fittings for my SCBA tanks to use them for trail air.

Worst case, replace the valve on your tank to an inert gas valve.

That one from MSC is just the one I need, but looking to get it in SS or steel for the extra factor of safety, and it doesn't seem like they have it. Thanks for the help, regardless this should get me there.