Silver Brazing-thanks To Bruce Evans

[Dan Metsker]

Silver brazing not to be confused with silver soldering. I've always wanted to branch out into hidden tang blades, but I was always up against the problem of how to properly attach a threaded rod for the maximum strength to the stub tang. I've tried pinning it, etc.

I know that many makers just fire up their wire feed welders or the oxy/ace tanks and away they go. The problem I have is that my situation doesn't allow for the oxy/ace tanks. The pursuit continued. I finally picked up the nomenclature difference between what some people were calling hard solder as actually silver brazing. In checking silver brazing is very, very strong joint.

Further investigation hours spent in finding out about this. I want to thank Bruce Evans for his website and all the generous information his site contains. After reviewing his site I SUDDENLY picked up on what the man was saying. Here is silver brazing at its best!

Next problem I had was a heat source. Discovered that there isn't that much difference in flame temperatures between MAPP gas and acetylene. Acetylene burns dirtier and needs the oxygen hookup to burn hotter. With MAPP gas and the right burner head, you can easily get the steel to silver brazing temperature to ensure proper capillary action for the silver braze wire. You don't even need the oxygen cannister. MAPP gas is available at most hardware stores.

It took a while to find suppliers of the silver brazing wire I needed and the special flux, but once found and put it all together--it is a push! Of special note to those that may try silver brazing (almost as strong as a weld)--make sure your mating parts have been degreased without contamination. After this I'll be shifting to hidden tangs for the majority of the future knives I make--

Just thought I'd give back some that I learned from the pro's on this site--Dan

[Alan L]

Congratulations! It's a very useful tool, glad you figured it out.

The following is not a slam, please don't take it as such; it's just more information to help others along.

Originally Posted by Dan Metsker

Silver brazing not to be confused with silver soldering.

Actually, it is the same thing. The problem arose when lead solder was banned for use with plumbing. Now lead free plumbing solder says "Silver-bearing" on the label, and that confused people into thinking it was silver solder. It isn't. It's soft solder with 2%-4% silver in it.

Originally Posted by Dan Metsker

I know that many makers just fire up their wire feed welders or the oxy/ace tanks and away they go. The problem I have is that my situation doesn't allow for the oxy/ace tanks. The pursuit continued. I finally picked up the nomenclature difference between what some people were calling hard solder as actually silver brazing. In checking silver brazing is very, very strong joint.

Hard solder is the term that has been used for well over a hundred years in the jewelry industry. It comes in several grades of hardness, each with different strengths and melting temperatures in order to make it easier to fabricate multi-part objects. The different grades flow at anywhere from 900 F to 1450 F, and have a tensile strength from 40,000 psi to about 70,000 psi.

If you want serious strength, check out nickel silver brazing rod. It contains no silver, of course, but it has a tensile strength of over 80,000 psi. That's 10-20,000 psi more than most electric welding rods/wires can do. It flows at a higher temperature, something like 1650 F or so.

I found out all this for the same reason you did, I didn't have an electric welder and I really suck at oxy-acetylene welding. :

It's a really good trick to have in your knifemaking skillset, for sure!

You can also use the nickel brazeing rod to repair broken steel objects that will have a polished finish, as the braze is the same color as the steel.

The nickel silver rods or the hard hard (as opposed to easy or medium) silver solder is what I use to seal the bowls onto my pipe hawks after threading them on. Soft solder would work, but the hard stuff makes me happier.

[Dan Metsker]

Thanks Alan,

no offense whatsoever taken, the more information the better. I concur with your analysis of the "silver solder". I'm using a product called Safety-Silver 45% (comes in a coiled wire form) and the companion Stay-Silv Black Flux for high temperature areas. It is rather difficult to find and it does have 45% silver content.

I've tried using the nickel silver rods you refer to (I usually find them in the hardware stores that are packaged by Bernzomatic. Actually they have very little if any silver and a heck of a lot of nickel that melts at a much higher temperature than the Safety-Silver 45%. The higher heat does tend to take more of a preparation to avoid disturbing the heat treatment of the blade. I can see where you would need the nickel rods for the pipe hawks.

Still whether you call it hard soldering or silver brazing, the choice of the consumable material is the real key.

[Alan L]

Exactly!

I like safety-silv 56 too. It's all good stuff.

The Eutectic corporation makes several alloys, including one that matches the color of German Silver/nickel silver fittings. Bruce demo'd it once, and I've forgotten the part number for it... One of the many reasons I stick with sterling for fittings, I can match the color!

That's one of the things I love about this stuff, you never run out of stuff to learn (or forget!)

[Rocket_Jason]

You mentioned needing the right burner head... What's the right head to use?

-Jason

[Dan Metsker]

Jason,
I looked for the Turbo mix head--that way I don't need to match an oxygen tank up with it. It draws its oxygen from swirling the outside air to mix with the Mapp--hope this helps.

[Miles Undercut]

Anybody know how to hard solder/silver braze a guard onto a blade without losing the temper? If so, please post a detailed step-by step. Everything I have seen on this, from Loveless-Barney's kiss-off of a book (don't bother telling me how wonderful it is, I have heard it already) to the excellent Blade Magazine book and articles, kind of slides past the details. (Seems to me even with Stay-Brite you are going to put enough heat into the blade side to cause some weakening....) MANY Thanks!

[Alan L]

Miles, (is this THE Miles Undercut of Los Alamos?) as far as I know nobody hard solders/brazes guards on unless the blade is an alloy (one of the CPMs or other super-stainlesses, for instance) that can take that heat. Soft or low-temp silver-bearing solder, yes indeed.

If you have a good electric kiln you could braze on the guard before HT, provided you are HT-ing a simple steel that austenitizes around 1450-1525 degrees F and your brazing material flows at 1650 or higher. You can see why good temperature controls are important there...

For regular solder, there's the wet rag technique, the heat-blocking paste stuff (which I've never been able to bring myself to trust), or even suspending the blade in a glass of water while heating the guard/blade. Somebody around here even uses a big ol' electric soldering iron with a shop-made tip that slots around the tang under the guard. That's a much more controllable and mess-free way to go than a torch.

I don't solder many guards, but when I do I don't worry about taking the temper out of the blade that much because I like the idea of the guard area being at a spring temper rather than fully hard anyway.

The solder thing for guards is really just as a moisture seal anyway. That's why many folks now are using JB Weld instead. Ideally the guard should have some sort of mechanical lock if prevention of movement is a concern.

The way I see it, if swords, etc. never used solder for the last 2000 years there must be a reason.

[Miles Undercut]

Curses! My cover is blown! Yup, 'tis I, but not Los Alamos-- except for visits to The Black Hole. I am in Tesuque. Okay, many thanks!! I might try it with Heat Fence forward of the guard and the paillons of silver solder, coming in from the tang end with the heat. And strongly consider guardless designs.