How best to fix a partly failed Silver Solder joint?

[Ian S CParticipant @iansc]

I can use a carbon arc torch on the stick welder, it works ok, wouldn't use it for silver solder.

Ian S C

[IanTParticipant @iant]

I'd not heard of ceramic fibre "rigidiser" before Peter – but I've checked online and found a source of this for £15 (a litre). As I stated (above) earlier, the ceramic blanket does seem to stiffen up after use but if there is a danger of airborne particles when using it 'as-is' – then perhaps additional treatment is a good idea.

I've been using my new Bullfinch 404 propane torch recently by the way. It works just as well for silver soldering – getting assemblies up to heat noticeably quicker than my disposable gas torch (and I suspect is much more economical in gas too – but time will tell).

These laser-cut 2.5" locomotive building frames (thank you Malcolm) had their base-plates (about 4" x 3" ) SIF-bronzed and this went OK (well the second one went better to be honest) – so I'm happy that it will generally handle the size of smaller brazed assemblies that I wanted it for – locomotive and tooling/jig parts etc.

However, when I came to assembly the uprights to the baseplates (a fairly large assembly) there wasn't enough heat to braze the whole lot together – almost but not quite ( it's about 4" x 3" by 8" tall ) – so I pickled the 'failed' attempt overnight and the next day silver-soldered both of them. They were done from inside the back uprights and the solder flowed easily through the slight gaps at the bottom but it didn't come right through the tab & slots on the uprights quite so well (I'd left them a force fit). I have decent enough fillets on the other side though – so they are pretty solid.

Regards,

IanT

[Ian S CParticipant @iansc]

If you have a smaller torch, and decide it's not big enough, keep it, use your new big torch to bring the job up to heat (it's handy to have a mate to hold the torch), then using the smaller torch, apply the heat to the joint to get it to brazing/silver soldering temperature. then go and have a cupper.

Ian S C

[IanTParticipant @iant]

My workshop activities tend to be pretty solitary in nature Ian.

This was a relatively large assembly – with lots of surface area to radiate the heat away.

I did think (very briefly) about using a charcoal bed to keep the heat up for the SIF brazing (LBSC used to use a coke bed for his boilers) but decided to simply lower the temperature requirement by using silver solder instead. Apart from a DIY-type disposable torch – I do also have a butane torch with various nozzles, including a flame spreader. I might well try to rig a clamp (third hand) for this torch to provide some extra heat input for larger bits in future.

Regards,

IanT

[Ian S CParticipant @iansc]

IanT, a third hand is the way I have to go, as I'm solo here, gee I wish I had three arms at times.

Ian S C

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