3/4" Raritan 2-4-0 build.

[RET]

Hi shild,

Soft solder and silver solder are totally different worlds and the techniques used are very different. Most people know how to soft solder (electrical experience, soldering gun, etc.). but that doesn't necessarily help you with silver soldering. Greg's instructions are a big help and I would recommend that you try to follow them, but the one thing he didn't mention is the fact that you need a fairly bright red heat to do it. For most things, you will find that 1/16" dia. wire is best, although you can also use a vise to flatten the wire into strip and place that between the parts. Silver solder is strong and you only need a little. Make sure the parts are clean and bright and that any galvanizing has been thoroughly removed. I would recommend that you practice on small non-essential parts first until you perfect your technique.

Use quite a bit of black flux on the parts and get them a bright red before adding any solder. When the temperature is right, touch the silver solder to the joint and it will flow into the joint and largely disappear. Once you learn the technique, you will see that the solder will follow the torch and you will be surprised how little you need.

For locomotives, you use silver solder for two reasons. First because it flows well and is very strong. Second, at boiler operating temperatures, soft solder isn't safe because you are too close to the solder's softening and melting point, especially where the crown sheet is concerned. Remember, if there is any soft solder at all, silver solder doesn't work.

One final word of advice. You are too obsessed with speed.

With your size mill, .020" is a HEAVY cut unless you are cutting plastic. Even with my Bridgeport, a lot of the time I only use .020 or .030" cuts because I get a much better finish together with good accuracy. Yes, I can put a 1 1/2" dia. carbide insert cutter in the head and run the spindle at 1,000 to 1,500 rpm. With that setup, when I take a 1/16th of an inch cut on steel it will throw blue chips all over the place and give a bright finish at a high feed rate. I don't do that because it makes a royal mess of everything. Besides, those blue chips are hot and hurt when they hit you!

My Bridgeport weighs almost exactly 2,000 pounds, pretty close to ten times what your mill weighs so don't expect major machine tool performance from your machine, it just can't do it. Remember, if you ask Harold, a Bridgeport is still considered to be a "light" machine tool!

Hope this helps.

Richard Trounce.

[Steamer Al]

Thanks Greg, Thanks Anthony. I'm still confused about why I've never needed silver solder to solder copper wires together but need it for this build? Is it only when I do steel to steel that I need it? Or do I only need it for the boiler and can get away with regular solder for the unpressurized tender tank?

I suggest doing research as the the difference between soft "silver bearing solder", and true "silver solder/brazing". You'll learn much more finding and researching the literature, like Kozo's material.

Perhaps a book like this is a good start, if you dont have something similar already:

https://www.abebooks.com/products/isbn/ ... g=gw_2_qcp

[Steamer Al]

You remind me so much of myself when I started my airplane years ago. I was young (20 at the time), excited, full of energy just to get it done. It took me a while to realize if I was going to do a good job, that I could be proud of, I had to force myself to slow down, take my time, learn all I can about what Im doing, and most of all, just enjoy the BUILDING aspect of it. On my model project now, I just enjoy the few minutes a day I get to spend downstairs in the shop, and take huge pride in making my models precise and look nice.

Built right and well maintained, your locomotive will last forever. Slow down now, and you'll be very thankful in the future.

[Greg_Lewis]

To add and reinforce what Richard wrote above, the difference between silver solder and electrical solder is the alloy. Electrical solder is most often a mix of 60 percent tin and 40 percent lead. There are also lead-free electrical solders. These have melting temperatures between about 370 and 460 degrees F. As lead and tin are soft, they are also weak mechanically. Electrical joints don't, or shouldn't, require much mechanical strength. OTOH, silver solder, which is most accurately called silver brazing rod, does not contain lead. The alloy I like is 45% silver, 15% copper, 16% zinc and 24% cadmium. (I prefer the cad alloy to the cad free.) This alloy is much, much stronger than the tin/lead alloy and will adhere better to steel than the latter. It's going to need a melting temperature of about 1145 degrees, which means it will remain strong when part temperatures are high. (And, obviously, that temp. is too high for many electrical applications.) It is not uncommon for mechanical parts to get up to, say, 300 degrees in operation, which weakens electrical solder. Go much over that and the joint will fail.

And Richard mentioned clean metal for good joints. That needs emphasis. Clean, clean. No oxidization, no oils, no coatings of any kind, no fingerprints. Nothing but bare, fresh, clean metal. If you clean the metal and quit for the night, clean it again the next day before soldering. I have a beadblast cabinet (You can make one from a plastic tub) and as long as you never use it for greasy parts and clean off the blast dust, it's a good way to clean the parts. But degreasing, then sanding with clean paper or emery cloth and a followup with acetone is just as good.

[Bill Shields]

Acetone....clean with acetone..no waiting

[Builder01]

Has anyone mentioned pickling solution for cleaning up flux and oxidation before and afterwards? I use citric acid, others use sulfuric acid. I don't think anyone had mentioned the reason for the use of flux, is to prevent oxidation of the base metals during the brazing process. Extreme heat oxidized metal, flux prevents this. Oxidized metal will not allow for the silver solder to flow. This may all seem obvious, but, it might be worth mentioning.

[RET]

Hi shild,

Like Greg, I also use the cadmium version, it flows easier and as the name implies (easyflow), it is easier to use. I've been doing this for 40 years with no ill effects. On the other hand, if I were building a boiler, it probably wouldn't be such a smart idea.

Another characteristic of silver solder is that the thinner the joint, the stronger it is. Even although you aren't welding the joint (welding is when the parent metal is melted and flows together), if the joint is only a few thousandths of an inch thick, the joint strength can be almost as strong as the parent metal. If you look on line, you should be able to find test results that confirm this.

I buy my bandsaw blades in 100 foot coils and because my bandsaw doesn't have a blade welder, I make a lap joint on the blade ends and silver solder them together. I cut the blade from the back (soft side on a bimetal blade) with a pair of heavy tin snips, and grind the lap joint ends on the blade. I then clamp the blade ends to the open table saw extension to hold everything in place for the silver solder operation. I wouldn't have a prayer of doing that with soft solder, it just isn't strong enough, but with silver solder, it works.

Builder01 is correct, insufficient flux or flux in the wrong place will prevent the solder from sticking. The flux keeps the parent metals from oxidizing; the solder has to "wet" the metal first (steel, whatever) and the solder can't do that if the metal is oxidized. That is also why the metal has to be really clean first, the flux just keeps it clean while soldering.

Hope this helps a bit.

Richard Trounce.

[NP317]

Shild:
Soldering electronics wires together normally uses "37/63" solder: 37% lead and 63% tin. This is "eutectic" alloy with the lowest possible melting temperature for electronics soldering. As the percentages of tin/lead change (either way) the melting temperature rises.

Our locomotive construction requires structural solder, with far greater strength than electronics solder. Thus the addition of silver.
"Safety-Silv 45" solder has 45% silver in the alloy. This provides significant strength, enough to hold copper boiler parts together under pressure use.
Hardware stores sometimes carry "silver solder" but close inspection of the packaging MIGHT reveal that it only contains 5% silver, far too low for functional strength.
I have no use for such solders.

And 45% silver solder melts at temperatures that produce red color in the metals. The melting temperature is actually high enough to be in the "brazing" range, as I have noted before. Thus referring to "silver brazing."

And I often order silver soldering supplies from Amazon online. Any apparent "higher" prices are far outweighed by getting the correct materials the first time, without having to drive (far distances for me) and spend time and gas money. Works better/cheaper for me.

I hope this helps answer your questions.
RussN

[shild]

Thanks for the replies everyone! Richard that's amazing you get silver solder to hold your bandsaw bands! But it's never as strong as welding is it? But anyways I got several more cuts, holes and a couple of solderings down the road. No I didn't use proper silver solder, but I'm still learning to solder with a torch, maybe I should be learning with lower temperature regular solder first on something not so critical like this tender chassis? Can always weld anything that comes undone here can't I? Next thing I plan to do is solder those endplates onto the center beam. Anyone have suggestions for how to hold them in place?

[NP317]

Use a variety of clamps and/or fixtures to hold parts together.
Or follow Kozo's examples and use brass screws to hold parts together while silver brazing them. ('Order one of his books yet?)

One problem with using low strength solder: When those joints fail, it is difficult to fully remove the old solder. It will contaminate whatever you use next (hopefully structural strength silver solder) and result in a faulty joint. It is always faster to do it properly the first time. I know from personal experience...
RussN

[Greg_Lewis]

...
No I didn't use proper silver solder, but I'm still learning to solder with a torch, maybe I should be learning with lower temperature regular solder first on something not so critical like this tender chassis? Can always weld anything that comes undone here can't I?
...

Silver soldering isn't the same as low-temp soldering. The tricks and techniques you will learn (the hard way... there is no other) aren't the same. And if something needs to be silver soldered, then welding would most likely not be the way to fix it if something goes wrong. And don't use low-temp solder on the tender chassis if silver solder is specified. Low temp solder would only be good for cosmetic parts that have absolutely no mechanical stress, and even then silver soldering often yields a better looking result. I find low-temp solder just doesn't flow as well as cad alloy silver solder.

[Steamer Al]

Thanks for the replies everyone! Richard that's amazing you get silver solder to hold your bandsaw bands! But it's never as strong as welding is it? But anyways I got several more cuts, holes and a couple of solderings down the road. No I didn't use proper silver solder, but I'm still learning to solder with a torch, maybe I should be learning with lower temperature regular solder first on something not so critical like this tender chassis? Can always weld anything that comes undone here can't I? Next thing I plan to do is solder those endplates onto the center beam. Anyone have suggestions for how to hold them in place?

Why dont you learn to Silver Solder on something similar, but not so critical like some cut off ends of the metal you used to make the tender frame? Then you can get it right so you dont have to learn on something critcal like your tender frame.