Need info on a good oxy/acteylene set up for brazing

[bulgie]

O man I looked at a Meco Midget - very nice and very spendy too.

I didn't know they were expensive, I got mine for free. I bought a gas fluxer, which adds liquid flux into the fuel line before it gets to the torch. ("The flux is in the flame!" is their motto.) Anyway I bought one used off ebay, very crusty, cheap because it was so ugly (nice now after a rebuild), and it came with a Meco Midget attached, that the ebay description didn't even mention. Also crusty and beat up, but also plenty nice now after a rebuild.

The Midget is amazing, so small that your hand covers it almost completely, with just the neck tube that goes to the tip showing outside your paw. And yet it takes tips that make a big roaring flame if that's what you want, even a rosebud is available. It's a proper aircraft torch, not a jeweler's "little torch". The neck tube comes in several lengths, with the long one recommended if you're using really big flames, to get your hand farther from the heat. The gas and O2 knobs are right there under your fingers, super easy to adjust while welding.

But I keep coming back to my Smiths AW1 for most things, probably because that's what I grew up using. I can't actually think of any reason not to like the Midget.

 

[ddickey]

It’s fine to shut off at the torch when preparing the work.

I was taught to shut off at the torch when done, then at the tanks. Then bleed acetylene first then air. But that’s just my dad.

You’ll pretty quickly get in the habit of shutting valves at the tank the first time you run a full tank down to empty by leaving one open.

John

And back out the regulators.

 

[helmbelly]

I didn't know they were expensive, I got mine for free. I bought a gas fluxer, which adds liquid flux into the fuel line before it gets to the torch. ("The flux is in the flame!" is their motto.) Anyway I bought one used off ebay, very crusty, cheap because it was so ugly (nice now after a rebuild), and it came with a Meco Midget attached, that the ebay description didn't even mention.

Nice snag, they like $250 on ebay. I wanted one but got a Uniweld 71 on Marketplace for $65 with a #0 tip. Is using a gas fluxer like the cat's meow? Just curious.

The gas and O2 knobs are right there under your fingers, super easy to adjust while welding.

Are you using small hose? I think you said it's flex tube which sounds great. My 71 has the small 3/8 sockets which I guess yours prob also has. I should prob switch out to Type A flex hose with the smaller fittings. (to be clear I say Type A thinking that is the smallest gas hose I think 1/4" which I would also think saves fuel) I don't like the adaptors I just bought - they tend to leak and I lost a few bucks of Oxy yesterday. I want to use a small amount of thread seal, someone mentioned green teflonlike tape. I gotta use something

That said what seemed to help finally get a braze yesterday was lowering A to 4lb pressure and O to 5, then I made the inner white cone a little longer I can't remember if I added O or took away A but it was a longer, cooler flame. Seemed to help.

 

[helmbelly]

Silver doesn't like gaps, strength drops off a cliff when the gaps get over a few thousandths.

Clearance is tight 3-5 thou at the top joint but squirley at the bottom joint on the stock threads. Prob need to keep stainless as it's for an exterior bike product, and the threads need to be stainless.

Would you consider brass brazing them? Brass fills gaps well, but doesn't like to wet out on stainless, so you'd have to make the handle out of plain steel (or alloy like 4130 if you need the strength).

It's a two piece thing so I could make the handle of plain steel and then powder coat it with the threads masked off. Are you saying Stainless will brass braze to mild steel well? I'm more used to anodizing alum but if so, there may be ways to weatherize steel "handle" component short of powder coating.

It takes a different flux, but brass flux is better at lifting oxides and other contaminants, so brass brazing is a lot less demanding of cleanliness. (Note, what I call brass is called bronze by the welding industry. Don't get me started! But I'm right and they're wrong! Just shop for bronze filler rod and they'll send you proper brass.)

This is crazy - I have craploads of machinable brass rod- you mean plain brass is ok for brazing (and it's actually bronze) ;-) I'm gonna try this and see what happens

Some people seem to like flux-coated rods and/or powder flux but not me, I only use paste flux. The stuff they'll sell you at the LWS is probably sub-par, so I'd get some "Type B" flux from GasFlux Company.

roger that- and thanks

You can get your filler rod from them too. I like their C-04.

copy

Huh, I just noticed they say C-04 can be used on stainless — never tried it, maybe I should. I don't remember if gasflux.com has minimum order sizes that are unfriendly to hobbyists, but if so you can get small amounts of their stuff from Framebuilder Supply.

copy copy copy. I'll call these guys Monday and report back so other people can hear what they say about C-04 on SS

Another option is the rod misleadingly named nickel-silver — which has zero silver in it. It's a bit higher-temperature than brass (opposite of silver) but it sticks to SS, and it's super strong. The filler itself is about as strong as mild steel. It can use the same flux as for brass, but Cycle Design sells a flux specially formulated for nickel-silver. Their website doesn't look like much, but they're a reputable company, I like their filler and fluxes and they've given me excellent service.

This is a lot of really good stuff to run down. If youre ever in New orleans I know a joint that still makes the old time gumbo and you're money is no good there.

 

[helmbelly]

I don't know what you mean by a knife switch or guillotine. It has spring-loaded valves that are open ("on") unless the weight of the torch pulls the lever down. The stand was made by me in about 30 minutes, from qty 4 of 2 ft long, 1/2" (ID) plumbing pipe, and a 3-way 90° elbow that I tapped another hole in, for the pipe that goes up. You need to have a tap for 1/2" pipe-taper threads. Put threaded caps on the three legs facing down, and a "floor flange" on top, which the gasaver bolts to. I also added a 10 lb weight that was free at a neighbor's yard sale, for extra stability, but it was pretty stable without the weight.

By guillotine or knife I just mean the simple up/down gravity on/off. BTW that's a hell of a good stand. I was staring at it going 'plumbing pipe, good do-dinger backyard engineering' then going 'no, brass fittings, manufactured'. Well done. If you can make that in 30 mins I'm frankly depressed. I would draw pictures of it for the better part of an hour. Maybe 2.

 

[bulgie]

This is crazy - I have craploads of machinable brass rod- you mean plain brass is ok for brazing (and it's actually bronze) ;-) I'm gonna try this and see what happens

I recommend not doing that. Stuff sold as brass tends to be brass (copper/zinc) not bronze (copper/tin), but there's other stuff in it too, like lead. Since it wasn't formulated for brazing, it might be terrible at wetting out, or adhesion, or...? Try it if you want — with excellent lung protection and no one else around to breathe the lead — but not on anything where strength of the joint is critical. I don't know what-all goes into making good brazing filler, but it is highly engineered stuff, probably for reasons.

 

[helmbelly]

I recommend not doing that. Stuff sold as brass tends to be brass (copper/zinc) not bronze (copper/tin), but there's other stuff in it too, like lead.

yup, I have 260 and 360 from McMaster. They define 260 as

"260 brass has the following chemical composition:

• Copper: 68.5–71.5%
• Lead: 0.07% max
• Iron: 0.05% max
• Zinc: Remainder"

I have bronze and brass welding rod so I'll stick with that. Appreciate the lead warning. Guy at LWS gave me 5, three foot rods of differing types for $2.

I'm starting to wonder about brazing brass tube to a brass stud. Bronze welding rod would be right? Do you know a flux?

 

[RaisedByWolves]

It’s fine to shut off at the torch when preparing the work.

I was taught to shut off at the torch when done, then at the tanks. Then bleed acetylene first then air. But that’s just my dad.

You’ll pretty quickly get in the habit of shutting valves at the tank the first time you run a full tank down to empty by leaving one open.

John

What about backing off your regulators?


I shut off tanks and back off the regulators, then bleed fuel-oxygen.

 

[matthewsx]

What about backing off your regulators?


I shut off tanks and back off the regulators, then bleed fuel-oxygen.

Yes, I forgot that step. Back the regulators all the way off so they don’t get hammered next time you open the tanks.

John

 

[helmbelly]

Better results today. I cleaned up an old piece of railroad tie and put a firebrick behind it. With this I can work inside at a bench - where I have discovered a new form of flying insect that doesn't seem to bite ;-) I cut a couple pieces of 25/64 tool steel that fit tight in the two "arms" which seem to help equalize the heat. First photo below broke when tested clamping down the handlebar clamp. The second one seems quite strong. Yesterday I was doing it in dim light to try to see the steel go dull red. Today I'm under a bright light paying attn to the flux turn glassy - it's still tricky, it comes up to temp the silver melts, you try to add some more but already it's got too hot, the flux goes black and your busted. So tomorrow when that silver pools I'm gonna try to back off the torch and keep feeding the solder. When it works it's like magic.