Silver soldering

Hi all,

It has been a long time since I last posted here. Anyhow, I have been going over some of the past few weeks postings to catch up...

I am currently building a lady stephanie beam engine. I am currently making the 'eccentric rod'. It is suppsed to be made from 1/16th MS, but I couldn't find any, so I have now made it from 1/8 x 3/32 stainless. Quite a bit bigger, but it was the smallest cross section I could find.

Anyhow, I have now made the 'struts' for want of a better term. (This is where the bars strenghten the eccentric rod and I suppose looks a little like a truss).

I am now ready to silver solder them, but having never done any silver soldering, am looking for any tips. (I have done brazing in the past, but then I was working with a proper brazing hearth with firebricks and what have you. I don't have anything like that here in my own workshop).

I have a brazing torch and also a small gas torch (like a pencil which takes cigarette lighter fuel). I have silver solder and some white flux powder for it. How do I use the flux? Do I mix it into a paste like with the flux for brazing?

Same as any sort of brazin really, make sure you have enough heat (Ive never found anything small enough to braze with those gas lighter pencil torches), all components are clean and dont apply direct heat to the flux.

I warm the rod enough to make the flux stick then when the work is hot enough I apply it to the work keeping heat on from the torch, but again heat the work not the rod.

Play about wih some scrap to get a feel for it for first, you'll find it just works.

Steve

Hi,

Thanks, I will try it (tomorrow evening now when I finish work).

Do I need to mix some flux with water as I seem to remember having to do that with brazing... (I do recall when I was doing the welding phase of my apprenticeship, also dipping the warm welding rod into flux (gas welding) to get some flux in, however, my apprenticeship was 23 years ago and I moved out of commercial engineering 19 years ago, so everything is hazy.)

I use easiflow flux and I've never mixed it with water, when the flux meets the hot components it tends to flow. Self taught, not aware of fluxes you mix with water. Dad used to do a fair bit of brazing with brass rod's no recollection of him mixing flux with water either.

Steve

Easyflow flux is usually supplied as a paste to mix with water although it can be bought ready mixed. However it is not very good for stainless steel. Better to use Tenacity no.5 or HT5.

Have a look at this website for some good advice:

regards, Russell.

I manufacture an assembly made from brass and copper which is silver soldered.All the joints are fluxed before heating with Easiflow made into a paste and painted on the joints.It helps if you add a couple of drops of washing up liquid to help it "wet" the metal.Pic of the finished assembly here.It`s the red manifold about halfway down.

Hi,

Thanks, I will be bookmarking that site.

It does say on there to mix the flux with water to get the consistency of yoghurt.

I am not sure what flux I have. It is a white powder, I am guessing it is not HT5.

cupalloys is actually fairly local to me (about 15 miles), so in theory, I could pop-up and have a look. Surprised thought that there are no prices on the site for silver solder (or none that I could see.)

Thanks for your help.

Miine is a white powder - and I got it from cupalloys.

Steve

You might find some useful information here...

If you ring up you'll also get some helpful advise.

Ahhh,apologies the link has already been posted.

Allan

I did read somewhere that mixing the powder with meths as opposed to water stops it hissing bubbling and blowing around when heated. Not tried it but does the pencil / graphite trick stop the s/solder running where you do not want it? Suggested a while ago re tin/lead soldering.

Graphite will just burn off at brazing temperatures

Tippex works OK

Thanks for that, need to S/Solder the crank for my "Otto" soon and wish to minimise the spread.

Yes, but make sure you get the traditional solvent based stuff (now called Tippex Rapid), not the namby pamby water based one.

Russell.

The silver soldering flux I use is a white paste ( of course I'm in Australia so brand names are useless to you) heat both the components to be joined and apply the paste flux ,it will sizzle a bit and dry out to a powder keep heating until the flux melts into clear liquid ,now apply your solder rod ,it should melt and flow where ever you placed the flux. I must add that the material being joined should be nice and clean with no oxidization .

You can also get flux coated silver solder rods ,but they are more expensive .The higher the silver content of the solder the more expensive as well ,but it makes nice jointsand flows better .

Over heating the silver solder will cause it to bubble and will give a lousy looking join. Silver solder does not need the same amount of heat as brazing. If one component is larger and heavier than the other apply most of the heat to the larger component.

Forget the pencil torch a LPG (propane) torch or oxy /aceteylene is best using a neutral flame.

Practice on scrap with the same type of joint that you will use on the real job, you will find that when you get better with practice little clean up and filing will be needed .

Kev

Moving away a bit from fabrication, how do the experts clean boiler parts beforehand ? Presumably NOT emery for boilers as it might cause pin-holes ? Even steel wool might leave bits behind ?

Peter

Well, I have jumped in at the deep end and done it now.

For my first attempt, I am very pleased.

I soldered half of the thing togethor, then I was doing the other half, heating it up and the first half collapsed. :(

I then changed my strategy. Get the first half done as before, then the second half, do opposing ends first, then the bits in the middle. This worked.

When I have finished cleaning it up, I will put a photo of it online.

Hi fellas, I need your help. I'm also starting my brazing/soldering works. In my case, I will need to join small diameter brass tubes together (0.5 mm to

2 mm). I'm working on a model plane in 1/100 scale (not RC) and I prefer to make a landing gear in brass than plastic, cause it's a bit large and heavy bird, so the plastic tubes would bend with the time passing. I already have a butane pen torch, but I don't know which silver solder is proper to this use. Which percentage of silver is recommended? And which flux I must use?

Thanks in advance. Cheers, Joao

Just about any silver solder you use will be as least as strong as the brass. I'd recommend Johnson Matthey EasyFlo powder flux. For the size of materials you are using, put a teaspoon full of flux in an egg cup, add a _small_ drop of washing-up liquid, and drops of water until the mixture has the consistency of double cream. Make sure the joint is clean and free from oil/grease, paint the joint with the flux, and carefully heat it until the flux bubbles up, clears, and settles down. Now remove the heat and place a small piece of (barely) fluxed silver solder on the joint. Carefully heat the joint again (don't heat the solder directly - if you do it will melt into a little ball and refuse to run into the joint) until the solder melts and runs into it, and the job is done. It should take longer than a few seconds, 10 at the most. Prolonged heating will burn the flux and render it useless. The above technique is used by jewellers; I've used it for over 50 years 'cos I'm a jeweller. If your silver solder is a rod, flatten the end with a hammer until its about 0.25mm thick, and cut a piece off about 1

- 1.5mm square. That's the size you need for the size of joint you described.

Thank you so much Gary! ;) I will try to do that as soon as I can. These guidelines are very precious for me.

Cheers, Joao

P.S.: Sorry the late answer...