Silver Soldering/Brazing Technique

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Chucketn

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I have a noob question on Silversoldering/brazing. I have only silver soldered 1 part in my life. Ihave a part that press fits together with finger pressure. It's ashaft for a crank, and the other part is a flange for the crankbearing. Is this type of fit 'loose' enough for silver solder towick/wet between the parts?
Should I flux the mating surface ofboth parts before pressing together?


Chuck
 
I always put flux and both parts and then hit the silver solder up with a little heat and then dip it into the flux as well. It does not take a lot of solder either. Make it "flow" with the heat to get it to cover all the areas that you want. Think some people just try to glob it in. A good fit up and flow is what you are after. Just my 2 cents. Good luck
 
Hi Chuck
Be sure both parts are super clean, no oil (finger prints) Scratch the surfaces with light emery paper/cloth and it should be a slip fit, no pressure, but not loose, maybe a thou. clearance. You might even put a few scribe marks for the silver braze to flow in. If you use an oxy/acet. you wanna be sure you don't heat it too hot. A bushy flame
will keep the heat down. I haven't used it but a lot of fellas use mapp and seem to have good luck if the object isn't too large. Get a couple of scraps of the same material to practice on if you're not sure. Good luck
dickr
 
It also never hurts to keep a little extra flux sitting outside the immediate heat zone in case you need it. A lot runs off when it starts to liquefy unless the part has some sort of shelf to catch it, and some off to the side will be warmed up a bit. Silver follows the heat, so just add a bit at a time so you don't goop it up, and try to put heat where the silver needs to go. Hope that makes sense. That's my experience building bicycles with lugs, anyhow.
 
I forgot to mention that lower silver content will fill gaps better. 56% is better when the fit is closer and 45% better if the fit is looser, but if too loose, silver isn't a good idea.

-Ryan
 
I used to solder wave guide for a living and probably made tens of thousands of hand soldered joints on mostly X-band guide. It was pretty tricky because any solder that wicked into the inside corners of the guide meant signal attenuation and failure. Here are a few tips that I learned over the years:

Less solder means a stronger joint, so tight fitting joints are essential. Thoroughly flux both parts, inside and out and clamp them into position so they don't move when the flux melts, especially when working with a blind hole. I like the Stay-Silv line of fluxes. Heat everything evenly with a slightly carburizing oxy-acetylene flame and don't over heat the part. Use just enough heat to get the solder to flow. You'll know the part is hot enough to add the solder when it looks squeeky clean. If it starts turning black, then it's too hot. Once you get a small blob of solder to stick, just walk it around the joint with the torch, that's all it takes. Hot water followed by an etching with a phosphoric acid based metal prep will clean off all the flux and oxide. A nitric acid solution is better yet for brass, but hard to get and hazardous to use. You should have to look closely to see the solder on a properly soldered joint.

Have fun!

Tom
 
I hope that I am not stating the obvious, but remember that silver solder will take a lot more heat to melt than soft solder. some pieces I have had to heat to almost a dull red before the solder would begin to melt. Test often, and as soon as it melts, reduce the heat, and use just enough to get it to flow.
 
I make flutes. We silver solder all day long. When i have to put steel tools together, i try to put some solder in the cavity, heat it up, and push things together. Usually the solder will show at the seam. Add solder if necessary. File off excess. The Wolverine Ultra
Flux sticks to the surfaces a little better than other fluxes. Sometimes i file a flat on a part, lay down solder on it, clean off the flux, and mate the parts. There are lots of ways to effect the joint.
Payson.
 
I want to thank all who have commentedand offered advise on the techniques of silver soldering/brazing. Alot of good info to think about and apply.
A little background on me. I havesoldered for electronics for many years. I actually taught highreliability soldering for the USAF for many years. I have also donesome plumbing soldering over the years using propane and mapp gas,even an old kerosene blowlamp. I have only silver soldered/brazedonce, and can't find that part now! So, I am familiar with theprocess and what solder flow and wicking look like.
I have my Dad's Proto torch set,regulator and acetylene tank that I intend to use for silversoldering/brazing. It needs a new hose, as the original is lookingdry rotted and I don't trust it. I'm looking for firebrick to make ahearth, and have found a local supplier for the solder and flux, anda replacement hose.
I have uploaded a photo of the parts Ineed to silver solder/braze.


http://i571.photobucket.com/albums/ss157/chucketn/DSCF1344.jpg


The part, shown assembled at the top,and the 3 components at the bottom, is a connecting rod for a modelsteam engine. The clevis on the right end does not get soldered. Theflat part on the left gets soldered to the end of the rod in theposition shown at the top. The rod part is run of the mill 3/16”CRS rod, not modified other than faced in the lathe and threaded forthe clevis. The flat piece is 1/16” crs plate, drilled and tapped2-56 on the outaide holes and drilled 3/16” in the center.
As made, the flat piece is a lightpress fit on the rod. I used a ball pien to tap the rod into the flatpiece on the anvil part of my bench vise to get a flush fit. I cantwist and pull the flat piece off the rod with my fingers. I used a3/16” drill to make the mating hole. If I use a #12 drill the flatpart is loose on the rod.
Hope this clears up your questions andgives you a mental picture of what I'm trying to do.


Chuck
 
During my research for my silversoldering project, I cam across the .pdf linked below. It has goodinfo including pictures of a reducing flame. I had run across severalreferences to a reducing flame but this is the first illustrationI've found.
www.richard-whitehouse.co.uk/Soldering%20notes.pdf


Also found firebrick at Lowe's.

Chuck
 
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