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Silver Soldering

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Wolfie06/01/2012 18:03:37
502 forum posts
OK another thing to learn sigh

Right as I understand it its similar to electronic soldering except you use a blowlamp and heat it up to a higher temperature.
Can anyone recommend a silver steel and flux combination?

Edited By Wolfie on 06/01/2012 18:03:49

Ramon Wilson06/01/2012 18:36:09
1319 forum posts
382 photos
Hi Wolfie,
Solder - Easy flo
Flux - Easy Flo
Three parameters in strict order
CLEANLINESS - no oil or greasy marks
Flux - mix the flux with some clean water to a thin paste and coat both parts.
Heat - heat the part until the flux appears to flow like water - do not apply the solder near the job before the flux gets to this stage otherwise you will melt the solder all over the work - result, lots of cleaning up to do. You can apply more flux to the job by just heating the rod and dipping it in the flux powder (not the pre mixed paste) but be careful not to melt the rod. When the flux flows like water gently touch the rod to the join and, if the heat is uniform, the solder will flow all round the join
Make sure the parts are not tightly fitted as the solder needs to run through the join by capillary action.
Quench the parts when they have cooled sufficiently - too quick the solder may still be fluid, to long and the flux residue will tend to harden.
It's simple enough but veryeasy to get it wrong when you first start. Do some practice parts first
Remember - Clean it - Flux it - Heat it - Then put the solder on .
Last week I spoke to the guy who taught me this when I was fifteen - 52 years ago

Hope this helps


Edited By Ramon Wilson on 06/01/2012 18:38:56

JasonB06/01/2012 18:50:12
22747 forum posts
2653 photos
1 articles
Ramon only problem for Wolfi is that now its 2012 its illegal to sell CAD bearing Silver Solder (in the EU)
So you will need silverflow55 or the CuP alloys No 455 both of which contain more silver which helps combat the lack of cadmium. I'd also suggest the higher temp Tenacity 5 or HT 5 flux particularly if you start doing larger fabrications as it lasts longer if you are heating for a while.
Wolfi have a read about silver soldering on Cup's site

Edited By JasonB on 06/01/2012 18:51:32

Edited By JasonB on 06/01/2012 18:53:42

Ramon Wilson06/01/2012 19:57:31
1319 forum posts
382 photos
Hi Jason, thanks for pointing that out and sorry for misleading you Wolfie.
The technique hasn't changed I hope
I guess it's still okay to actually possess the stuff or heaven forbid have I been breaking the law today I hope not - theres an awful lot of it been squirreled away over the years
Regards - Ramon
Wolfie06/01/2012 20:04:45
502 forum posts
No worries. I've been reading that cupalloys stuff and it pretty much concurs with what I read in a book this morning. So I'll get one of their starter sets that will do me for this part for my engine anyway.
JasonB06/01/2012 20:13:31
22747 forum posts
2653 photos
1 articles
The Cup Brazing Tips also apply to silver solder so worth reading as well.
Please see my comment about that video on the plans thread, better off just not looking at it as its too contradictory to our type of soldering and darn right dangerous.

Edited By JasonB on 06/01/2012 20:13:58

Stub Mandrel06/01/2012 21:32:57
4315 forum posts
291 photos
1 articles
Johnson Matthey website is quite good too.
Clive Hartland06/01/2012 22:10:56
2820 forum posts
40 photos
One thing Wolfie is that make sure that you have enough heat output from your heat source.
For the small eyelet you have mentioned one of those small gas canister lamps will do but if you need to braze/silver solder a large piece of metal then you will need a much larger gas torch.
Terryd07/01/2012 02:59:17
1936 forum posts
179 photos
Hi Ramon,
Just shows how advice can contradict. When I was training to be a teacher, I elected for a jewellery/silversmithing course as one of my units (2 years, one day a week) as I already had much engineering experience. The very experienced lecturer taught us to make joints by fluxing and adding small snippets of solder called 'pallets' I think. As the flux boiled and heated just before the glassy stage obviously these pallets moved but were coaxed back into place in the now molten flux with a long thin stainless or soft iron probe Solder won't stick to soft iron as it oxidises..
Trying to add the solder from a long stick, it is tempting to try to apply it through the flame and of course it melts before reaching the joint. With small joints it is possible to move the flame away and use the residual heat to melt the solder but that involves higher heats as heat loss can be quite pronounced. It is also the reason most folk use a larger torch than is strictly necessary. Of course the largest structures we would solder were tankards or coffee pots but the same methods for (admittedly small) boilers works for me.
As for flux we used pure borax (inexpensive) from a jewellers cone and dish , grinding it to a paste in the wet dish using the cone like a mortar (dish used as pestle) and applying with a brush. We used this with quite large copper items for practice as well as with precious metals. To prevent excessive solder spread (essential with precious metals) we used a loam/water or jewellers rouge mix as a resist. Now I use Tippex or soft pencil. This was especially important when soldering lengths of chenier tube to make hinges on boxes to ensure that the temporary locating wire within was not soldered or the lengths of tube soldered together. It was interesting stuff for a mechanical engineer.
I tried to embed a YouTube video but it seems not to have worked.  It won't even link to the page using a hyperlink.  Has anyone had succeeded in this on this forum?  The link is here:
Best regards

Edited By Terryd on 07/01/2012 03:27:43

Terryd07/01/2012 03:14:01
1936 forum posts
179 photos
Test for video

Success I think
By the way Wolfie, I just re-read your initial post.  You surely mean silver solder, not "silver steel"! 

Edited By Terryd on 07/01/2012 03:33:18

Terryd07/01/2012 04:17:00
1936 forum posts
179 photos
Hi Wolfie (and any interested members),
I accidentally came across this link to a modelling site in Australia which gives a good background into silver soldering (aka in the US as silver brazing), there is some good advice.
One point is important, which is shown on the site and that is to use proper refractory bricks to contain and concentrate the heat from your torch.   You will often be advised to use ordinary firebricks or even cement building blocks - don't - it is false economy.  As it says you will waste a huge amount of heat just heating up the blocks.  Proper refractory bricks absorb little heat and are white to give a 'reverberatory' effect i.e. they actually reflect heat back into the work, that is why kilns and furnaces are lined with white refractory materials.
Hope it is of some help or interest,

Edited By Terryd on 07/01/2012 10:12:34

mgj07/01/2012 09:31:55
1017 forum posts
14 photos
Tubal Cain is very good on it in his book. He advises, similar to the jewellers, the use of prepositioned bits of SS where ever possible, and I find that a very succesful technique - its actually the best way if possible or circumstances permit, because the SS won't melt until the metal is hot enough.
A few centre pops are a pretty good way of ensuring a small gap between two bits of metal.
Ramon Wilson07/01/2012 10:24:48
1319 forum posts
382 photos
Hi Terry,
Yes, I agree, there are always more ways to skin a cat but I was trying to keep it basic as Wolfie, now beginning another new experience, probably only needs sufficient information to solder up his inlet and exhaust pipes
The techique you describe is indeed another way - I think the small pieces are referred to as 'pellions' - as is winding up small rings of solder to apply to pipe flanges, rivets etc. before heating.
By using this method on small parts it can create the potential that you can end up with too much or too little on the join as the solder melts but it's horses for course really. However as for poking it with something - I'm not particulaly enarmoured with that thought if the parts are not pinned together in some way as they could easily be moved out of register.
I've just soldered up the flanges to the pipes for the Waller engine. The flanges had pre drilled bolt holes and the pipe was loose enough to allow the solder to flow - carefully aligned before soldering shows a situation where movement was definitely not required
The solder stick (from wire section upwards) should not melt as soon as it's brought into the flame. If the job has been brought to the correct temperature first, the flame can be moved just slightly to allow the solder to touch the join. Of course if the flame is big enough to build a boiler and the job is 1/8 pipe then you do have a point
Many having a go at silver soldering for the first time do not get the workpiece to temperature first, bringing the solder in too quick in the process. This does lead to melting of the solder and great blobs of it all over the place hence the advice to Wolfie.
Something else that may be of interest to some is that to remelt a soldered joint requires a greater temperature than the initial soldering. This characteristic can be used to great help if several small parts have to be soldered together as they can be done separately in stages. Using differing melting point solders will enhance that process even more.
Just a couple of further points that may help someone - trying to silver solder something that has previously been soft soldered will prove fruitless as the silver solder simply will not take. All traces of the soft solder have to be removed to be successful
On that note if you dont want silver solder to take to a specific area then before fluxing the join 'coat' the area with a soft lead pencil -one of those flat carpemters pencils are ideal.
As previously said - it's a simple process but one which can so easily look a mess
so practice first
Regards - Ramon

Edited By Ramon Wilson on 07/01/2012 10:30:14

Gordon W07/01/2012 10:30:01
2011 forum posts
Wolfy, all the above are good. I only learnt silver soldering a couple of years ago, although used to welding and brazing. It is much easier than electrical soldering ! Only thing I would add is to direct the heat onto the bigger part, or the part with the hole, the solder will flow to the hotter part, just as in plumbing.
Wolfie07/01/2012 10:41:29
502 forum posts
Thanks all plenty of info there. I have ordered a starter set from Cupalloy and I'll use it to try and solder my eccentric ring on. I'll practice on that.
I only have a blowlamp so I was planning to stand it up in the vise and attack it with that.
And yes Terry I did mean silver solder lol

Edited By Wolfie on 07/01/2012 10:42:02

maurice bennie07/01/2012 10:46:34
164 forum posts
1 photos
Hi Wolfie If you can go to local library .There are many books on jewellery making .
Showing how to prepare metal for hard soldering ,also to work the metal and hold small pieces with clips and pins to stop them moving. When you have mastered this many brownie points can be earned repairing family jewellery , or even making it. After I retired I spent one day a week for some years at classes I found it time well spent .
Best wishes Maurice.
P.S. "jewellery making" by Hamish Bowie ISBN07153 70448 for a start.
maurice bennie07/01/2012 10:55:02
164 forum posts
1 photos
P.S. Wolfie .Take great care of the area past the end of the flame ,and also above it .the heat will go a lot further than you think BEWARE please dont ask me how I know .
AndyP07/01/2012 11:09:15
189 forum posts
30 photos
Wolfie, If you grip pieces in the vice to solder them the vice will act as a heatsink and draw heat away from the job. Far better to prop or pin (dressmaking pins work) the job to a lump of refractory brick to stop them moving around if there isn't a good mechanical joint.
I have always known the little pieces of solder as pallions and if you place them wet and heat the job slowly so the flux dries rather than boils they won't all jump off.
A practice piece is a very good idea just to get a feel for how much heat is required and what the flux looks like when the job is hot enough.
Maurice has a good point, plastic bottles of flux do not respond well to an oxy/propane flame in my experience
Swarf, Mostly!07/01/2012 11:21:16
664 forum posts
73 photos
Hi there, all,
Regarding refractory bricks to localise the heat:
When our landlords condemned and stripped-out our gas fire, I hung on to the refractory 'radiants' with just this use in mind. However, I haven't had the opportunity to use them yet.
Best regards,
Swarf, mostly.
Ramon Wilson07/01/2012 22:28:00
1319 forum posts
382 photos
Hi Wolfie,
I have spent today finishing off an inlet valve, parts of which needed silver soldering so these may help a little.
The advice about anything acting as a heat sink is a sound one all the heat should go into the job especially if the heat source is a bit marginal for the job in hand.
My hearth is quite small - just the width of a standard fire brick. These do absorb the heat so the part is closed in with 'Skamoflex' a refractory material that doesn't (This is a previous pic not from today)
My version of the borax cone and ceramic dish
The valve top fluxed up ready to heat. The solder was applied by hand - 1/16 rod Easy-flo.
(Jason, if you are reading this has 'Easy' flo been replaced by 'Silver' flo ?)
The parts as finished ready to clean up. The major diameter is 14.4 mm, the 'bars' are 1/16 brazing wire
These parts are for the Waller engine stop valve - there are a lot more pics on HMEM if you or anyone are interested.
Good luck with your first attempts.
Regards - Ramon

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