Tinning a steel screw?

[Homercidal]

I'm looking at converting some stainless Fire Extinguishers into small kegs. Only issue is I have a couple of threaded ports I'd like to plug. One of them is a #2 straight thread and I'm pricing SS O-ring screws and they are pricey and hard to find.

Then I thought why not just solder a SS screw in there to seal it?

Then I thought, why not tin a regular steel/brass screw and solder it in there?

Any thoughts? I have some SS flux and some lead-free solder.

 

[k-moe]

Why not just use a buna-n o-ring on a pan head screw?

 

[Homercidal]

Why not just use a buna-n o-ring on a pan head screw?

That would be fine if I can find a SS screw that fits. Nothing so far in this small town. I may be leaving town tonight and if so I'll check the bigger stores.

I've actually already got a screw with an O-ring, but it's plated. I want to get rid of the plated screw.

 

[Homercidal]

So apparently a 1/8" screw is not the same thread as a 1/8" straight pipe.

 

[Homercidal]

Maybe I should just re-tap it for NTP and make it easy...

 

[jddevinn]

By #2 straight thread do you mean 2-56 Thread?

http://www.mcmaster.com/#93802a315/=11w6jqb up to 6,000psi rated

I'm interested in seeing the result of this.

 

[The_Bishop]

I don't know how good of an idea this really is. I use stainless extinguishers nearly every day, refill them too. They're not designed for 'sanitary' use.

 

[Yuri_Rage]

Silver solder will work better for you. You'll likely need a hotter torch than straight propane or MAPP, though.

 

[Homercidal]

By #2 straight thread do you mean 2-56 Thread?

http://www.mcmaster.com/#93802a315/=11w6jqb up to 6,000psi rated

I'm interested in seeing the result of this.

I don't know that much about all of the various kinds of threads out there, but this is what it is supposed to be. I checked with a brass nipple at work.

http://www.amazon.com/dp/B002689DWK/?tag=skimlinks_replacement-20

I don't know how good of an idea this really is. I use stainless extinguishers nearly every day, refill them too. They're not designed for 'sanitary' use.

This may be true. Having taken it apart, cleaned and inspected it, it seems fine, although not as easy to clean as a corny. I didn't see any problems with seams in the tank. The valve is a bit more complicated, but I still think it's suitable. it can be baked to sterilize after cleaning as well.

Prior to this last modification I used it to serve soda and it functioned fine. I wanted to make the connections more standard.

I have several different models, some of them have valves that may possibly be converted with some effort. Some are just empty tanks that make great 2.5 gallon secondaries. I haven't tried converting any of the others yet.

I *could* consider machining a new valve body out of something on the machines at work, but by the time you buy a pair of QDs, seals, the body material, and the time involved, a brand new small keg starts to look pretty inexpensive.

This is almost just for the fun of it.

 

[jddevinn]

I don't know that much about all of the various kinds of threads out there, but this is what it is supposed to be. I checked with a brass nipple at work.

http://www.amazon.com/dp/B002689DWK/?tag=skimlinks_replacement-20

Ah, OK straight thread... Hadn't heard the #2 designation, and 1/8-27 is very small!!! (note 27 is the thread per inch)

NPS = National Pipe Straight
NPT = National Pipe Thread

Both NPT and NPS have the same thread angle, shape, and pitch (threads per inch). However, NPT threads are tapered and NPS threads are straight (parallel). If this is NPS you should be able to thread a NPT fitting into it...it just may not seal correctly

1/8-28 BSTP (British Standard Pipe Taper) is more common....are you sure it isn't that?

If it is NPS I can't find a cheap/fast fitting that fits....I'd drill out and tap to fit one of the self sealing machine screws http://www.mcmaster.com/#machine-screws/=11w7gmb