Thread: Fright Today !

Are we talking about soft solder (tin/lead) or real silver solder?

Originally Posted by irony

I've found the best way to do that is to grind a slight cone on the end of the hex shaft, drill a hole in the extension piece slightly smaller than the hex key and force the hex into the extension with a bloody big hammer. I have several keys and centre drills like that I made years ago - none have ever let go. Horrible feeling thinking you've broken something - expensive, tends to make you more careful, for a short time at least.

Hi Irony,
Yes I agree. I must admit that the hole that I drilled was a little sloppy. I recall just measuring across the corners and choosing the nearest drill size. It was obvious that the solder had not run into the hole and only taken to the edge of the rod. Also the bit of hex had been bright plated, which didn't help. Annoyingly I've been using that key for several months.

One big lesson learn't ! Remove plating before soldering.

Originally Posted by Techo1

Are we talking about soft solder (tin/lead) or real silver solder?

I assume silver solder ! Its some that I've had kicking about forever (35 - 40 years ?) Its a very thin flat tape, my soldering iron won't melt it but my butane torch will. This time I used acid flux and filled the hole, then I heated the bit of hex dipped it into the flux. The plating on the hex rapidly disappeared. Another quick dip into the flux and pushed it into the hole in the end of the rod. The excess solder just pushed out and ran down the side without sticking to the rod. So I don't think it will loosen again.

PS. I do like the big hammer idea.

It seems to me that the acid flux that you used was not the correct one for silver soldering.Silver solder flux is a borax based paste that has the consistency of cream.If your flux has dried up add some tap water until it is about that.
In addition the silver solder is capable of a capillary action probably down to 6mm deep with the socket formed for the key.

The trick is to obviously clean the surfaces to be jointed with solvent and dry off.The flux paste is generously applied to the areas you want the silver solder to capillary to.

Keeping the s/solder well out of the way at this stage, heat the bits to be jointed concentrating more heat on the bigger, thicker component with more volume.The idea is to get both thee components to the same temperature so that the silver will bond to both at the same time.

In the latter part of this this phase, stroke the silver solder across the heated joint but not under the flame ,the inherent heat in the components is what makes the silver solder flow.
When the parts are hot enough the silver solder will wick into the joints in an instant.
Just heating the s/solder stick will just cause the end to drop off and not bond to the components.

When the solder starts to flow move the focus of your heat to around the areas your want it to flow to .ie the thicker section. Keep the torch moving as holding it in one spot for too long you can make the solder too hot and oxidise the zinc part of the alloy out of the silver solder thus ruining it.

Once you learn the knack it is like riding the proverbial bicycle.

Grahame

Hi Grahame,

Thankyou for sharing your expertise on silver soldering. I have to confess that the only soldering that I have done in the past 30 odd years has been electronics. The silver solder I have is many years old and quite dirty. I've heard about borax as a flux but I can't say that I have some because I haven't.

Anyway I've made a note of the information in your post so that I won't forget it.

Grahame covered most of it. Not to say I am an expert. Regarding the hole you drilled, it is a good idea to have some clearance for the solder to flow into.

Dean

Originally Posted by Grahame Collins

It seems to me that the acid flux that you used was not the correct one for silver soldering.Silver solder flux is a borax based paste that has the consistency of cream.If your flux has dried up add some tap water until it is about that.
In addition the silver solder is capable of a capillary action probably down to 6mm deep with the socket formed for the key.

The trick is to obviously clean the surfaces to be jointed with solvent and dry off.The flux paste is generously applied to the areas you want the silver solder to capillary to.

Keeping the s/solder well out of the way at this stage, heat the bits to be jointed concentrating more heat on the bigger, thicker component with more volume.The idea is to get both thee components to the same temperature so that the silver will bond to both at the same time.

In the latter part of this this phase, stroke the silver solder across the heated joint but not under the flame ,the inherent heat in the components is what makes the silver solder flow.
When the parts are hot enough the silver solder will wick into the joints in an instant.
Just heating the s/solder stick will just cause the end to drop off and not bond to the components.

When the solder starts to flow move the focus of your heat to around the areas your want it to flow to .ie the thicker section. Keep the torch moving as holding it in one spot for too long you can make the solder too hot and oxidise the zinc part of the alloy out of the silver solder thus ruining it.

Once you learn the knack it is like riding the proverbial bicycle.

Grahame

Lots of people call any thing with silver (%) in it "silver solder" , this could be yellow (5% silver), brown (15%) or some others

when doing steel Blue tip (45%) is the recommended stuff.

Graham I always thought that if you get it too hot you actually destroyed the silver ?...so its the zinc eh?

Yep! the zinc turns molten but cannot be over heated as there is only a very narrow temperature window for it to remain in a molten state.Exceed it and your zinc goes pffff!!! turns to gas and your have oxidised it. Same deal in bronze brazing as it also contains zinc
Understand that zinc is just but one of the components of silver brazing alloy. There are also can be Copper, Zinc ,Silver, Silicon, Nickel and Tin in various proportion according to the constituent parts of the particular SBA grade.

I know at one time there were up to a dozen grades of the SBA alloys including one for beverage lines that did not have nasties in it.
.Previously I failed to inform you about the cadmium content of the older type. I suspect it was possibly the cadmium that enhanced the free flowing and wetting ability of the older SBA fillers.

The new SBA (silver brazing alloys) are cadmium free.

I also have had a suffered of brain fade here as I failed to mention the current flux coated rods.I will blame the cadmium.

Many current SBA filler sticks come as flux coated.
They are supposed to be better than the liquid flux but I personally doubt that as I get better results from the liquid paste flux which is far easier to pre apply accurately to the places where one wants the SBA to flow to.

The coated rods avoids the need to carry separate paste . I don’t like them myself as you can’t place the coated flux prior to heating .

You can obtain them at dedicated welding shops and plumbing supplies outlets.

And yes the given silver percentage for a grade of SBA is what dictates the application but also the lesser percentages of silver can make for more difficult usage as the silver content drops.

I have found SBA 245 is the easiest to use.

I find using oxy acetylene as a heat source to be more efficient as the ability to pin point the flame makes for easier heat distribution.
I have silver brazed with LP but found it has limitations one of which might the Bernzomatic torch that I use that does not produce a concentrated heat.


In use SBA,s generate welding fumes: copper fumes, zinc oxide fumes
and nickel fumes.

Hope this helps

Grahame

Originally Posted by Grahame Collins

I also have had a suffered of brain fade here as I failed to mention the current flux coated rods.I will blame the cadmium.

Many current SBA filler sticks come as flux coated.
They are supposed to be better than the liquid flux but I personally doubt that as I get better results from the liquid paste flux which is far easier to pre apply accurately to the places where one wants the SBA to flow to.

The coated rods avoids the need to carry separate paste . I don’t like them myself as you can’t place the coated flux prior to heating .


Grahame

So I'm not the only one then. I hate pre coated rods with a passion! They are wasteful, and do not allow you to tailor the flux application to the job. There used to be two grades of brazing flux available for cast iron and steel, one was a tinning flux which was more aggressive and then the standard brazing flux for use afterwards.
Then again, the amount of brazing done today would be a fraction of what was done once so it has all been dumbed down and streamlined.