Brazing vs soft soldering

[dvm27]

Michael Mott mentions brazing vs soft soldering in a recent post. This begs the question how important is silver soldering at this scale? Do rigging stresses often cause soft soldered joints to fail? What other applications would favor brazing over soft soldering on our models?  In my experience, I have found that soft soldering is easier and has a higher rate of success than brazing but perhaps because I do it so infrequently.

Edited November 7, 2017 by dvm27
mispell

[jud]

I have brazed using brazing rods on sheet steel and cast iron, when I looked up the definition, silver soldering did fit into the definition I found. Requires higher heat, can be used for dissimilar metals and has high strength, requires a close fit up at small scales. My brazing around the Ranch using large rod and a full size torch, touching parts and a can of flux could fill gaps well, pre-fluxing would be required for close fits. When building up assemblies, I would think that the base structure would be better using brazing and then change to lower heat materials as the assembly progressed. All speculation on my part, based on my experience around the shop and what I have read. I expect and hope someone who has some first hand experience in using progressive lower heating joining products will step up with some comments. I have been slowly progressing towards building a LST at a large scale, " 1/50, be 6.4' long and a foot wide ', large so I can show detail, plan on using sheet steel for framing and hull using brazing  rod or spot welding, followed up with silver solder for details. That is what I have running around in my mind for that project, might find that there is a good reason I have not seen anyone else using such a method on this site. Considering the use of all-thread with nuts and lock washers as rib stiffeners and spacers prior to any welding. Brazing is a method I happen to like and have the tools to use brass rods, but heat can create problems for small projects and Silver Solder seems to be the norm and upper end of the heat desired.

 

[russ]

Greg:

I have said this before, but I think it is worth repeating. Soft soldering is akin to gluing two pieces together while Brazing aka hard soldering aka silver soldering is like welding two pieces to become one piece. Regardless of the stresses involved, which sounds more permanent and less likely to fail over time? Also, a soft soldered joint is difficult to hide whereas the hard soldered joint can be blackened and will be invisible. Once you learn to do it and have a little practice at it, it will become second nature to hard solder. Once I learned the basics of it, I could not figure out how I went so long without it.

 

Russ

 

[kurtvd19]

I have found that in almost all cases in static modeling silver soldering is not needed. 

 

I have found that stay-brite silver solder (J. W. Harris Co  #11000) is completely adequate for static modeling purposes.  It's listed as silver solder on the container but when it is opened and the instructions are unfolded it is called stay-brite silver bearing solder.  It melts and flows at 430 degrees F and has a tensile strength of 10,600 psi.  I defy anybody to put enough tension on a rigging line to exceed that rating.  The percentage of Silver it contains is shown as 3-6 percent and Tin at 94-97 percent.  It is lead and cadmium free

 

I can't imagine any need for more strength in a static model.  I do true silver soldering on radio controlled boat rudders and control arms.  But the stay-brite has been perfectly adequate for all the hand rails and other metal parts on even 1/12 scale r/c boats.

 

Stay-brite mimics true silver solder in the way if flows into joints.  It can be blackened using the same stuff used to blacken the joined parts.  It's also great for resistance soldering.  I found out with a lot of use that the liquid flux that comes with it works fine but I have switched to Nokorode soldering paste (flux) by M. W. Dunton Co. due to my being able to put the paste flux exactly where i want it unlike the liquid flux.  I also prefer it due to less oxidation and base metal distortion than with true silver soldering.

 

Kurt

 

 

[druxey]

Stay-Brite can be blackened? Well, apart from the issue of false advertising, I didn't know that! Good to know that it is lead-free. Thanks, Kurt.

[Dave B]

Thank you Kurt for the detailed explanation of what has worked for you over the years!  I've had the same questions lately.

Dave

[michael mott]

6 hours ago, druxey said:

Stay-Brite can be blackened? Well, apart from the issue of false advertising

Of course there are always exceptions to the rule, (he said smiling).

 

Kurt; Thanks for your clear definition of the difference between hard and soft soldering, which in my view is a more clear way of describing the process rather than the visual colour of the solder.

One other aspect of the differences is that when soft soldering the metal model parts, usually brass, copper, or nickle silver, the metal itself stays hard, whereas when silver soldering or hard soldering because of the higher heat involved, the metal model parts that are being soldered get annealed or softened.

 

Michael

 

 

[Richard Griffith]

Thank you Kurt, Russ and Michael for the clear outlines.  I have to try the Nokorode idea........

 

Stay Brite is also my first choice when I need a very strong join, such as rings and mast caps, and for certain types of clamps that I make.  

Tix is another good choice (from Micro Mark and others) that melts at an even lower temperature, favored by jewelry makers.  It has its own flux too.  

 

Soft soldering is useful for large joins and for filling or adding large radii but is problematic for coloring and in cleaning the join, as stated above.  

 

Mr. K. C. Foran gives an excellent outline of his soldering techniques in his book "Model Building with Brass" ISBN9780764340048.  His models are top of the food chain.

 

The one critical rule is cleanliness.   Then practice, and practice some more.          Keep building and above all, have fun             Duff

[Landlocked123]

Hi Gents, 

 

Russ turned me on to silver soldering a few years ago.  I use a pen style butane tourch and paste solder that comes premixed in a syringe.  And Russ is right (above) that silver soldering becomes second nature.  There are few benefits that I find worth mentioning. First, there is essentially no wait time for the iron to heat up, one click and I have heat.  Second, with the paste solder/flux I can apply pin head sized amount precisely where I want with a toothpick. The joint flashes over in a second or two.  Finally, it takes a higher temperature to remelt the soldered joint, so it is quite easy to add a nearby additional joint without affecting the first.  I will still use Tix occasionally, but generally only if I’m soldering very close to wood or Britannia metal.

 

Best,

John

 

ps.  I use silver solder mostly for convenience, not strength.  J.

Edited November 9, 2017 by Landlocked123