Silver braze/solder questions

Tommegow

Tommegow

Joined
Dec 16, 2004
Messages
678
I decided to try to learn silver brazing after the post last week. I went to several local HVAC suppliers. The counter guys look at me like I had a horn growing outta my head when I asked about silver soder rods. Basically
they had 5% 15% and 4?% rods. I am assuming the higher the silver content the solder the softer joint ?!? They said no flux needed for the low % content rods.They also said I had to use an O/A torch not a LP torch. If LP burns at 2300 degrees isn't that enuff for brazing??
Thanks
 
Propane will reach 2300 but with forced air and some refractory along with much more volume then a torch produces. Just to solder aluminum I use MAPP or propylene because propane just takes too long. I believe aluminum melts at around 1218.
 
You pick a brazing rod depending on what you are going to braze, what the melting temperature of the rod and even the color but not by how much silver is in it ! Take a course usually found in local votech schools .A propane torch can be used providing the material is thin. Thick stuff requires too much heat [not just flame temperature] so you need oxy-propane, MAPP, or best oxy-acetylene. Remember [or learn ] that brazed joints are strongest at .003" thick and at that thickness capillary action makes the brazing alloy flow nicely into the joint.A .003" joint will also be hardly visible !!
 
Sorry but the last silver solder post was talking about hard silver vrs soft silver rods. I was trying to find out what the folks were talking about.I'll call the tech school for info from now on. (I did take a hobbist welding course there but we only covered stick and Mig, O/A cutting.)
 
when silver soldering, i usually prefer to coat the entire edge of both pieces with flux. then i cut small pieces of silver solder and heat them until they become tiny spheres. i then placce them along the joint (cover about 1/4-1/3 of the surface to be soldered with balls), in the flux, and begin heating the surrounding metal. the flux will dry out and then begin to melt and flow. soon after the solder will melt and flow into the joint. and that's it. you then let it cool and pickle it. this is the method i was taught when taking metal sculpture courses in college. my teacher had a background in jewelry and i noticed that his solder joints were always pristine. stick soldering can get messy fast as the stick can heat up more than you want at times. with the sphere method, you just add another one if you find you need more.
also, a propane turbo torch should be fine for silver, but oxy-acetylene is much better for brazing. hope this helps.
 
Tommegow said:
I decided to try to learn silver brazing after the post last week. I went to several local HVAC suppliers. The counter guys look at me like I had a horn growing outta my head when I asked about silver soder rods. Basically
they had 5% 15% and 4?% rods. I am assuming the higher the silver content the solder the softer joint ?!? They said no flux needed for the low % content rods.They also said I had to use an O/A torch not a LP torch. If LP burns at 2300 degrees isn't that enuff for brazing??
Thanks
Click to expand...

The low silver content solders you mention melt at around 400 to 600 degrees. This is not brazing.

Silver brazing is done with silver solder that has a silver content around 45 to 50% silver. The melting temperature for that solder is around 1400 to 1450 degrees.

Any torch will silver solder.

I've never seen silver soldering rod. It's usually sold as wire or in case of the high content brazing material it's also available as thin strip.

If you want to solder a guard on a knife shank, most people use the 5% silver solder.

Also, any solder must be fluxed.
 
I'm not sure what they've got, but you can silver braze with a propane plumbers torch. It just takes longer and for me makes a mess. I use a tiny jewler's tip atachment to my oxy propane rig. Tiny little hot flame just where you want it.
 
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