# Soldering/Welding Techniques

#### jpanhalt

Joined Jan 18, 2008
10,277
@shortbus
I agree with shortbus. The most important variable in "soldering" ss hypodermic stock was heat control. A little manufacturing oil did not affect results. The 601B flux I mentioned above is that brown color. I have almost no experience with it, which may mean it is better, and I just haven't tried it.

#### cmartinez

Joined Jan 17, 2007
7,100
That is what is so good about the StaySilv white, it has a change that tells you when the temp is close to the correct level. https://www.harrisproductsgroup.com/en/Products/Alloys/Brazing/Fluxes/Stay-Silv-White-Flux.aspx

I worked at 4 different places that we did jobs using silver solder, and Harris was the only brand any of them used. And these places were from "mom and pop" shops to GM.
So, what about the technique I used? That is, I wrapped a ring of solder around the rod, and making contact with the other piece, and then I applied flux to it. Then I torched the whole thing. That means that I didn't wait until a certain temperature was reached before applying the solder, since the solder was there from the very beginning.

And it worked. But I'm wondering if it's proper practice or not.

#### jpanhalt

Joined Jan 18, 2008
10,277
So, what about the technique I used? That is, I wrapped a ring of solder around the rod, and making contact with the other piece, and then I applied flux to it. Then I torched the whole thing. That means that I didn't wait until a certain temperature was reached before applying the solder, since the solder was there from the very beginning.

And it worked. But I'm wondering if it's proper practice or not.
What you did is similar to "oven brazing." It's a great technique and is widely used in production. Ovens provide great heat control

#### Bernard

Joined Aug 7, 2008
5,657
I use propane & oxygen with a Burnz-O-Matic old torch for every thing from 5/8 steel all thread with bronze to SS ring repair.

#### KeepItSimpleStupid

Joined Mar 4, 2014
4,229
The Sta-silv flux dries out easy. Put it in a better container or at least put a zip lock bag on it.

You won't solder anything with a heat sink (Vise) that big.

Don't apply heat to the solder. Heat the part.

Clean promptly. Boiling in baking soda usually works.

With your current setup, can see an improvement.
Try supporting the ring side with a nut and screw. Very loosely thermally couples/

You have way too much thermal mass sitting on the vise.

#### cmartinez

Joined Jan 17, 2007
7,100
I've just bought this kit:

And I'm thinking about buying these canisters for testing, although they're MAPP and oxygen, and not acetylene and oxygen. But I'm guessing it shouldn't make much difference since the temps needed for silver soldering are not so high anyway.

Also, does anyone know if the fittings on the previous kit will fit the canisters? Is the use of regulators essential?

#### cmartinez

Joined Jan 17, 2007
7,100
The Sta-silv flux dries out easy. Put it in a better container or at least put a zip lock bag on it.
Will do. Thanks for the tip.

#### TeeKay6

Joined Apr 20, 2019
572
Test #2. I used #30 Ga (really thin) pure sterling silver. It didn't work.

Here's how the part looks with the flux applied.

The picture below clearly shows that not enough temp was reached for the silver wire to melt.

Test #3. This time I used medium alloy (70% Ag) #20 gauge silver wire. It's easy noticeable that the wire's way too thick for the part.

And it didn't work either, also for lack of enough heat.

My problem is now clear. I need a far better torch than the puny toy that I've been playing with. I'm setting my eyes on something similar to this:

Now that I've found a miniature torch, my next question is, where can I find miniature oxyacetylene tanks? The only ones I know are humongous!
The contact between the "tab" and the vise will cool the "tab". Support the tab a little above the vise surface with something (e.g. a short piece of steel wire--no flux) to reduce the contact area between the "tab" and the vise.

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#### shortbus

Joined Sep 30, 2009
7,963
I've just bought this kit:

And I'm thinking about buying these canisters for testing, although they're MAPP and oxygen, and not acetylene and oxygen. But I'm guessing it shouldn't make much difference since the temps needed for silver soldering are not so high anyway.

Also, does anyone know if the fittings on the previous kit will fit the canisters? Is the use of regulators essential?
View attachment 181746
Not sure but you will probably need to use a bigger than normal tip with the MAPP since the gas BTU available is different. Don't know either about the regulators, but do know from my use of the jewelers torch they only need a minimum pressure, almost the smallest you can get with a standard regulator set.

To answer about using the ring of solder, I would put the flux at the joint and then the solder on top of that. It's the joint you want to clean, not the solder. And that is how the high end bicycle frames are made, but they put a ring of solder inside the tube and heat it from the outside, until they see solder in the joint. Many other things are done this way too.

I thought you had a shop? To build your machines. How do you survive with out a oxy/acet torch set? It is one of the first things I bought for my DIY shop, and is used for more than welding in fact I very seldom use it for that at all.

#### shortbus

Joined Sep 30, 2009
7,963
The Sta-silv flux dries out easy. Put it in a better container or at least put a zip lock bag on it.
My jar is over 50 years old. Like I said earlier when I need to use it a little water on the top of the flux and stir it up and its good to go. You don't need to stir up the whole jar just the very top surface. It is basically just Boric Acid with a few others things added. That, boric acid, was used in blacksmith/forge welding for centuries.

#### cmartinez

Joined Jan 17, 2007
7,100
I thought you had a shop? To build your machines. How do you survive with out a oxy/acet torch set?
I design and assemble machines, controllers and also write the code for their software and firmware. My tooling is limited to saws, wrenches, screwdrivers and taps (other than the electronics equipment) ... and yes, I own a Dremel tool (that I use a lot) and a bench press for drilling (that I seldom use). In fact, probably the tool that I use the most in my workshop is a vacuum cleaner. Things would get pretty messy quite quickly otherwise. Everything else is outsourced. I don't have a lathe nor a milling machine, and I don't think I'll ever get one of them either. Shoemaker to your shoes, I say. And if I try to do too many things I won't have the time (nor the skills) to make them right.

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#### cmartinez

Joined Jan 17, 2007
7,100
Good news. I've just found a local supplier for the disposable gas tanks and all of the accessories I need. And they're even cheaper here than in the U.S.! ... For instance, it's only about $45 bucks for a torch kit and a MAPP and Oxigen canisters compared against$65 at Home Depot in McAllen Tx...

#### KeepItSimpleStupid

Joined Mar 4, 2014
4,229
My jar is over 50 years old. Like I said earlier when I need to use it a little water on the top of the flux and stir it up and its good to go. You don't need to stir up the whole jar just the very top surface. It is basically just Boric Acid with a few others things added. That, boric acid, was used in blacksmith/forge welding for centuries.
I know it re-constitutes. I used stuff that was white. But, it's a pain everytime. I put it in a real chemical jar that seals and it did not dry out.

I was the best silver solderer at work, but never did really small stuff. The stiff @cmartinez is doing might require a jewlers's torch.

#### cmartinez

Joined Jan 17, 2007
7,100
The stiff @cmartinez is doing might require a jewlers's torch.
yeap ... that's exactly what I've bought, and I'm just waiting for it to arrive...

NOTE: "stiff" ???? ....

#### cmartinez

Joined Jan 17, 2007
7,100
Update

I bought myself this morning one of these kits:

And although the miniature torch I ordered hasn't arrived yet, I couldn't wait to test it. So I arranged things for the soldering process, and after lighting up, mixing in the oxygen and adjusting it until the flame looked the way it should, I applied the heat directly at the joint, and both pieces turned bright red hot after only a second or so. I stopped when I noticed that the wire had completely melted. Then I waited about a minute before cooling the part in tap water.

Here are the results.

This is the underside of the part in which I slid a ring of #30 ga sterling silver wire through the rod at the center. It can clearly be seen that the silver flowed from the top through the gap.

And this is the top side, in which the silver spread out a bit more on the flat piece before flowing into the rod's hole.

Here's the complete assembly. Thankfully, I did things right and it has the mobility that I planned it to have.

So the next question now is, how do I remove the ugly black finish? Through passivation? I read that it involves dipping the part in nitric acid. And I'm a little afraid of handling that substance.

#### jpanhalt

Joined Jan 18, 2008
10,277
What you want is a simple way to remove "slag." Particle blasting (glass beads or walnut shells) is often used. Walnut shells are very moderate compared to glass beads. Chemical methods do include nitric acid, which is surprisingly ( to me) inactive against steel.

Chemical methods will leave a smoother surface; whereas, abrasive cleaning will leave more of a mat surface. Molten salts (e.g., molten KOH) and nitric acid sound a lot worse than they are. Nitric acid is volatile. The one common acid I dislike using the most is sulfuric acid, as it is
non-volatile.

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#### SamR

Joined Mar 19, 2019
2,602
Wire brush time.

#### cmartinez

Joined Jan 17, 2007
7,100
Wire brush time.
I considered it, but the part is way too small. And also, a chemical method should also remove residue from within the gaps and joints, quite possibly resulting in even better mobility. The part in question is a special hinge.

#### KeepItSimpleStupid

Joined Mar 4, 2014
4,229
Boil in baking soda and water about 10 minutes ASAP. The longer it sits, the harder to remove.

If you have the option: Sandblast (glass beads)