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Thread: Silver solder stainless ?
04-05-2009, 01:49 PM #1
Silver solder stainless ?
I need to join two M6 stainless nuts to a 1.6mm thick by 10mm wide stainless steel band to form a clamp to use on a kayak paddle shaft joiner. Can one silver solder it, as TIG welding it tends too ruin the thread as I am not experienced enough to get good results when TIG welding it.
Any suggestions or recommendations are welcome.
04-05-2009, 02:19 PM #2
I dont know exactly what you are making, not into kayaks myself, but you can silver solder stainless steel. I do it all the time and I use a wire solder and flux from Weller. The solder is 56% silver and the flux is a white borax flux. Practice a little and it should solder with no problems, its up to you though to determine if the joint is suffecient for what you want to do.
04-05-2009, 03:09 PM #3
Thank you. What I do is build rather high tech kayak paddles with technology very similar to what is used in the aero space industry, started out as a kid 35 years ago building paddles and still at it. Thanks once again.
04-07-2009, 11:15 AM #4
I used to silver solder gas delivery systems using SS hypodermic tubing. I found that with the small pieces of tubing it was very easy to over heat the SS and create an oxide layer that the sivler solder would adhere to. You could peel it off if this happened so the joints were not reliable. Mostly, I have silver soldered SS with no problems though, it's just that thin small stuff that gave me grief.
04-07-2009, 01:54 PM #5
Mnay thanks for the advice, but thin as in how thin??
04-07-2009, 04:22 PM #6
Thin like in hypodermic tubing thin. The tubing had wall thickness of only a few thousandths and would heat up very quickly.
04-07-2009, 04:59 PM #7
I use Harris Safety-Silv 56 (in a pre-fluxed rod) for some stainless applications and Harris Safety-Silv 40 with Stay-Silv white flux for others. For the most part I use it for stainless tubing applications. I have used both for stainless to steel, stainless to copper and stainless to stainless applications. Either one should work for what you describe or one of the many other silver alloys available. Either a welding supplier or a refrigeration supply wholesaler should have the Harris products. Some of the alloys come in a kit form with a small coil of alloy and bottle of flux which would keep the cost down for a trial run.
04-07-2009, 06:22 PM #8
the original poster is in South Africa- I dont think Harris has much distribution there.
Me, I have had really good luck Tig brazing stuff like this, with a silicon bronze filler rod.
No special products, no flux, just generic silly bronze, which I have found everywhere in the USA, and suspect is probably available in SA as well.
Since you are brazing, not welding, you dont get the base material as hot, and it tends not to ruin threads. Of course, you need a tig welder that will go low on the amps- not all will, particularly older ones- and a light touch.
The resulting brazed joint, however, is very strong.
04-08-2009, 05:52 AM #9
I don't have a clear picture of what you are doing but is it possible to use a stainless steel Rivnut type of fitting rather than the silver soldered nut? Seems like it might be a simpler and cleaner installation.
Your paddle building venture sounds very interesting. I have inflatable kayak and a folding Feathercraft that I take with me on trips - great fun. Good luck with it and do you have a website?
04-09-2009, 08:13 AM #10
I,m not a great welder but.....
Brownell's gunsmithing supply house has a product, silver solder and flux in a paste, in a syringe(spl). Two different strengths. I use the weaker (and lower temp) to put sights on sixguns. Haven't had one come off yet.
04-09-2009, 01:10 PM #11
I have silver soldered or "sil brazed" stainless steels many times. I use the smallest possible tip and a very slightly reducing flame.
Here in the USA, I use the Harris products as noted in W. Snyder's post, above. I have also used a silver brazing alloy that comes in flat rods, possibly Silfos.
I do some fairly fine work and some involves joining bronze parts to the stainless parts. A go for the closest fitup, and pre-flux the parts before assembling to do the actual silver soldering. I use either of two alloys, depending on the type of joint and fitup. One alloy "wicks" into tighter fitups, on the order of 0.002" gaps. This alloy will tend to run out of any wider a fitup or spread over the heated surfaces of the work wider than needed. The other is more of a "bridging" alloy. This is used where more of a fillet is wented, or where the fitup is a little looser.
I usually move the torch flame a bit, rather than heat one single point to an excessive heat.
Another trick I picked up along the way came from a couple of men doing field rewinding of large power generators. Their work involved silver soldering and soft soldering of various copper connections. The connections took the form of multiple layers of thin copper, riveted, then soldered. To get things hot enough to draw the solder into these laminated sonnections, an oxy-propane torch with a small rosebud tip was used. This would heat a wider area, and the solder would tend to flow far beyond where it was needed. To confine the silver solder or soft solder to the area where it was needed, the winders painted a coating of Milk of Magnesia at the limits of the soldering. Milk of Magnesia is the same stuff sold in pharmacies. These guys had a bottle of it, and painted it on as a "stop" or "mask".
When the joint was up to temperature to "take" the solder or silver brazing, the Milk of Magnesia had dried to a chalky film. This stopped the flow or spread of the solder.
I have used this trick in silver soldering (or silver brazing) stainless steel and bronze belt buckle parts together. These are fairly fine parts, so the joints are closely fit. Given the design of the buckles, any sloppy work in the silbazing will show right up. The Milk of Magnesia trick not only keeps the silver solder from flowing beyond the joint, but it seems to protect the stainless from "sugaring" (getting that hard black coating from being heated).
04-09-2009, 07:22 PM #12
Check with a knifemaking supplier.Knifemaker's silver solder stainless guards to blades.You can find info at knifenetwork website.Hope this helps.Rick
04-17-2009, 03:45 PM #13
Most of the knifemakers are using a low temp solder, silver bearing is probably more like it with low silver content melting around 450+ F. Same stuff used in food industry fabrication.
Gunsmith & jewelry supply houses have high heat silver solders 1000+ F. and the right flux. Higher heat = more silver and stronger joint. Higher heat solders also need tighter fitting joints since it won't fill large gaps.
04-19-2009, 01:45 PM #14
Thank you all for advice given, I will be using it during the week.
11-03-2010, 01:19 AM #15
Just some feed back, used the info here and we now producing a stunningly good looking clamp. Thanks everyone.
11-07-2010, 06:08 AM #16
Well, lets see some photos!.............
01-21-2012, 11:14 PM #17
Well this is a trip down "where we were".
Found this posting and went back and looked at our first ones and those now.
But also want to share with you a tip how to neatly silver solder.
Put white "tippex" correction fluid all over / around where you want to solder.
Then let it dry.
Take the piece you wish to solder on , we now use a neat 10mm stainless machined round bar opposed to nuts.
Wet that piece and place it on where you want to solder.
That marks the area accurately.
We then sand that area with a tiny belt sander.
Put paste flux on and solder, we cut a small piece of silver solder and lay it next to the joint and it sucks into the joint.
When finished we soak it in acetone and all the excess mess flakes off.
Polish or soda blast and its done.
Just purchased a Colchester Chipmaster to speed up machining the small parts.
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