Silver-Solder Question

[gus]

Hi Gus,
I'm one of the guys with this double distinctions City and Guilds Motor Vehicle Restoration things and this was simply one of the competences.
Soft solder paste should be available at automobile factors who supply suitable lead for filling car body panels. You'll know the lead thing the same as me as you worked for Metal Box

As for the silver paste, mine came from Chronos in the UK but where else, I simply don't know. I would be having a word with your local dental mechanic, recalling that my late wife was an orthodontic consultant. Certainly, any dental tech. will know where to get borax as a flux. I had difficulty in getting borax from chemists because - it's a poison. However, I bought a clapped out MIG welder to restore and came away with a spare bottle of shielding gas and a jar of a sort of borax mixture which actually works.

Kills cockroaches as well- but I digress:hDe:

Regards

Norman

Hi Norman.

Thanks. Will buy tomorrow. Trust all is well at your end. Take care.

 

[gus]

Waymill is the companies name. I usually buy via their Ebay listings as their site does funny things on the international shipping calculations. They sell a number of different soldering pastes. From "Easy" (lower temp) through to Hard high temp and 75% silver.

https://www.waymil.com/mobile/Product.aspx?id=38847

As for hard soldering with MAPP alone, I had no luck. My setup involves fire insulating bricks. MAPP would never get even small parts up to hard solder temperature (1300F / 700c). Silver solder is much easier with Oxy MAPP. Even with Oxy MAPP it can still take time to get a part up to the point where the hard solder flows.

There are Mapp Gas Torch that come with twin torch or triple torch. I have seen Refrigeration Repairman using Mapp Triple Burner Torch to Silver Braze 3/4" Copper Pipe with ease. Foto follows.

 

[chucketn]

I have tried using Boric Acid, sold here in the US as roach bait, as silver solder flux. I could not get it to work.

Chuck

 

[abby]

Borax is the flux for brazing see earlier definition , it is not very good for silver soldering(hard soldering) .
Silver solder fluxes melt at a lower temperature than straight borax and contain potash (potassium carbonate) and flourides amongst other constituents.
Flourides when heated release hydroflouric acid which can be dangerous to health if working in badly ventilated areas.
If you can find a tried and tested recipe anywhere I will be suprised and grateful for a copy.
I have read the labels on dozens of products , looked at the specs published on line and done extensive googling but I have yet to find anything useful.
At the end of the day a commercially produced hard soldering flux is not expensive and for most people a 500 gm pack will last many years.
Manufacturers such as Johnson Mathey produce silver solder with varying melting points and fluxes for different substrates.
Some copper alloys such as aluminium bronze require a very active flux to get an effective join.

 

[bazmak]

Must disagree with the advice not to use oxy/acet.Yes it
s high temp and thats the point.With care it can get to the temp quickly and with local accuracy.If you take too long getting to temp and the heat spreads too far it make a mess of any joint.As an old school time served welder i never used anything but O/A.Even the real small delicate items with an accurate wave of the tourch and bingo.Yes you have to be careful of overheating but its far worse not reaching temp and trying to melt the s/s with the torch and not the job.As we should all know the job should be got to just red heat then melt the solder with the job.If you put the flux on first and take too long with the torch the flux becomes a black mess and thats bad.I prfer to ore heat local and melt the flux which should be a clear colour the heat to temp and melt the rod ON THE WORK. hope this helps Regards barry

 

[10K Pete]

Welding supply should have what you need. 45% alloy and white flux.

And I should add that all I've ever used for heat in silver brazing was O/A
for part large and small. It's a very hot flame, yes, but you have the control
over the flame size and application to the work piece. One must learn to use it.

Pete

 

[goldstar31]

Barry and Pete,
I must agree but we understand the skills in using a torch to get into the weld pool and remove the dross or 'dottle' which causes porosity.
Frankly, the skills of the old welders and other craftsmen are being lost and are being replaced with something which does not bear thinking about.

However, might I thank you for your attempts to get the message over?

Regards

Norman

 

[abby]

Oxy /acetylene is very useful but the cost of bottle hire and refills especially here in the UK would rule it out for most model engineers , I am lucky enough to have them but for most jobs I use propane .

 

[V22]

Oxy /acetylene is very useful but the cost of bottle hire and refills especially here in the UK would rule it out for most model engineers , I am lucky enough to have them but for most jobs I use propane .

And hence the Oxy MAPP. No bottle rental. Disposable cylinders.

 

[Korben]

Considering all the good information in this thread, cost, availability, and my immediate need (to braze steam fitting sleeves to 5/32" copper pipe), I'll start by experimenting with a Bernz-O-Matic type torch with disposable gas canisters. I presume that MAPP gas (without oxygen) produces a hotter flame than propane and would be the better choice.

 

[bazmak]

Yes the mapp gas should work well with with small dia tube to fitting etc
i have no trouble with up to 12mm sq but will try oxy/mapp next if i can find it
Does it work with the mapp torch i have ????

 

[V22]

Yes the mapp gas should work well with with small dia tube to fitting etc
i have no trouble with up to 12mm sq but will try oxy/mapp next if i can find it
Does it work with the mapp torch i have ????

Bunnings sell the Oxy cylinders. You will likely need a new torch. The oxy needs its own valve to meter the flow.. The MAPP torches that I have owned only have one valve.