So when I get back to school I will be hoping on the lathe and making a manifold for it. I have access to both steel and aluminum. Aluminum would be more readily available and much easier to work with. If I use aluminum I plan on making it inch and a quarter in diameter with a 1/2" hole running down the middle. If I use steel it would be 1" with the 1/2" center.

Would the aluminum be able to handle the pressure? My tank is only rated to 125PSI so I would not be exceeding that. Also would the threads be strong enough.

 

Both seem way overboard for a mere 125 psi. If the general shape is to be cylinder you could get away with the aluminum and a 1/8" wall with welded half threaded nipples. But assuming your feeding off the length I would be more worried with thread engagement (depth) if not welding.
Pressure rating for steel pipe http://www.ihservice.com/PDF's/Pipe%...on%20Chart.pdf
If you are worried with the threads leaking use BSP (British Standard Pipe) 5000 psi which has a straight thread and uses a copper gasket for sealing.
So simple answer yes aluminum will handle the pressure it is the shape of the chamber that is more important than the thickness. square corners are weak round holes are strong.
Here are some good links to get more info on pressure and how it effects different materials and shapes.
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just machine out a manifold out of a chuck of aluminum. this is what i made:

 

Kilby OBA manifold is Al, TONS of Jeeps (including mine) are running it for years.....Al is more than enough for that PSI...I run 160 in mine BTW.

 

Thats pretty much my plan, hence the thickness, it will be where the threads grab. Also those are the sizes that would be available for the low, low price of $free.99.

What I am worried about with aluminum is the threads pulling out, not the leaking.

Thanks for the information.

 

I wouldn't worry about it mang. Alunium is strong. I run 150psi+ is some of my aluminum parts i've machined out. It is strong. Heck, its used in airplane engines. Just make sure you have enough thickness around the holes you drill in it. And use a pipe thread. That way it seals it well. I like to use the thread sealent that is in a tube and goop out, although teflon tape would work fine.