Stainless to low carbon, 309 or fab the other part from stainless?

[Rambozo]

If you have a lathe, just get a nice stainless pipe coupler and cut it in half. I do that all the time for stainless pipe fittings. Way cheaper than making them from bar, and much faster. You can turn the OD to fit whatever hole you can bore in your tubing. Or you can fishmouth them if that would work better. Thanks to China there are now real cheap stainless pipe fittings, that you can make into all kinds of things. Here is a stainless manifold I knocked together from a bunch of pipe nipples for a fraction of what a pre-made unit would cost.



Took too long to post. You can get fittings in 304 or 316, at most pipe supply places.

[Trip59]

The ones on there are female... though after reading this, I'm wondering to myself; 'self, these are bungs to which fittings screw into, to which hoses clamp to. Why not just weld in tube the right diameter and put the hose directly on that?'

Any good online sources for these you'd recommend? Pretty slim pickins around here for off the shelf anything without driving half hour-45 minutes

[Rambozo]

Shipping would probably cost more than the part. Sure if it's just hose fittings, use some pipe or tube. Pipe would let you turn some barbs for better retention.

http://www.amazon.com/dp/B004XEKNBA

[Trip59]

The shop that made the on-the-road replacement without the fittings ran a bead around each end instead of rolling it. I was going to do the same on the larger pipe, the smaller... was thinking I could build up and turn down (harder to get a smooth bead around that smaller diameter). Guess it will depend on what I can find locally.

[Paul Moir]

Seems like a lot of work compared to turning down a bit of pipe. Plus turning barbs is kind of fun.
Alternatively back to the fittings, you can get a barb-to-whatever and take off the whatever and weld it on. Same plumbing supply place. (Or some gasket / steam places, and especially oilfield places come to think of it.)

The barb is just a retaining mechanism for the hose. It does nothing for sealing. One should be plenty if you put your hose clamp ahead of it.

[Trip59]

Main concern with evenness of the barb is stress on the hose. It does present little in the way of sealing, but if it protrudes or has pockets, etc. it could contribute to a later failure. Good point on using thicker and turning it down, I'll have to look into that option.

[Paul Moir]

Like Rambozo said, 304 and 316 are available. Locally they're mostly 316 for me. Either 316L or 308 filler would be fine. Whatever you have, assuming the exhaust was made of 304.

If you're welding steel to stainless, then 309 is technically correct. It has extra chrome & nickle to make up for the metallurgical soup you make joining mild steel to stainless (turning your soup into "not quite stainless but better than stainless dissolved in mild steel"). But in real life, 308 will work if you have some already; your soup will just not be quite a stainless.

Bungs down to 1/2" are common in the plumbing supply places, which is the only reason I asked. Smaller might be hard to find. Remember pipe sizes are nowhere near what you actually measure. (1/8" pipe threads are about 3/8" OD for example).