Pinning joints before silver soldering.

I'm OK with silver soldering in that I can make a sound joint between two pieces, but I now have a project which is more complicated - I want to make something like this:

It's two discs of CZ121 brass joined by horizontal CZ121 struts with a curvy bit of CZ108 between.

I don't think I can just assemble this on the brazing hearth and have away at it - something will move. So I wondered about pinning (or perhaps riveting would be a better word) in the locations shown.

Do you reckon this would work? I've no experience of riveting, but I'm thinking if I drilled countersunk holes and bashed soft copper rod in, it might hold it together for soldering.

Or any other strategies?

Robin.

Edited By Robin Graham on 23/07/2020 23:03:53

An alternative might be to bind the joints with soft iron wire.

... the solder doesn’t stick to it

The stuff that florists use is OK

MichaelG.

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Yes, wire might be enough to hold things together. It can be a bit fiddly to get the binding up right, though, particularly on small parts, and excess tautness in critical places can be as bad as, or worse than, not enough.

I've used pins numerous times to connect parts for soldering. The only caution I would give is that if you apply flux to the joints before heating, the assembly may still want to move apart as heating proceeds and the flux bubbles, whether the parts are pinned or not. This should be less of a problem when using pins, though, as long as they don't get pushed out altogether; just make sure you push the parts back into place before the solder flows.

Robin, A simple jig might help if wire binding proves too difficult.

Here's one I made to save buying more brass than I needed.

The large hole up the middle of the jig would be self explanatory. The brass bit was the maintaining detent for my skeleton clock.

Sam

Couple of 1/16" brass pins would do it, don't fully rivit them home just a quick tap to expand them enough to stay in place or even just bend them over, if you rivit them tight it will close up the joint gap too much. Solder will flow around the pins during soldering and excess can be filed off along with the pin after soldering so no need to CSK.

I'll quite often add a small screw or two to my multi part fabrications along with machining parts so they almost lock together with spigots, bridle joints etc.

Be careful if your setup puts any pressure on the parts as if you get a bit above soldering temps brass can distort if you have clamps ect squeezing too tightly.

Edited By JasonB on 24/07/2020 08:07:33

Is it possible to make the curvy bit slightly longer and wedge the ends in the corners between the disks and the straight studs? No need for rivets then.

You could do it in 2 stages, discs first and then add the curvy strip as a second op.

I'd use small holding screws on the four joint areas and do it all in one pass. On through holes, use slightly longer screws than required and machine (or file) off the heads and excess length afterwards. May not apply in this instance but sometimes it is useful to braze the parts before any final machining to size.

Being a Kozo Hiraoka devotee (certainly where silver soldering is involved) - I'd also centre-punch some 'dimples' in the joint areas and then not overly tighten the screws on assembly. This will allow the solder to penetrate the joint.

Regards,

IanT

Situations like this are very common in hand-made jewellery. Iron binding wire, as Michael suggests, is the standard method I use.

Clock tool shops sell assortments of tapered brass pins - used to hold the end plates of clock movements onto the pillars. Idea for the job in mind here as thery are very gently tapered, so stay in place readily, and a wide range of sizes.

Can't remember what they are called - something in French I think.

Cheers, Tim

Maybe "Clock Pins" Tim? - (or Épingles d’horloge if you want them in French)

Available here: Brass Clock Pins

Regards,

IanT

Thanks for suggestions - a few things to try. A couple of further questions about about the binding wire approach though.

First, what gauge of wire would be appropriate? The discs are 1.5" dia x 3/8" thick,the 'struts' are 3/8 x 3/16" to give an idea of scale. I see Cookson do 0.69mm binding wire, presumably for this kind of thing.

Second, why doesn't the wire stick to the work? I use Silver-flo 55 with Tenacity 5 flux which works well for steel parts as well as brass - is there something different about soft iron?

Georg49 - thanks for your input. It's likely that the design will change - my drawing was really meant to illustrate a general problem which I think I need to solve as I strive to tart up my work. It look's like you're a new member - if so, welcome.

Robin.

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That sounds a reasonable diameter, Robin

Sorry, I can’t explain in detail why silver solder doesn’t stick to soft iron : Presumably due to oxides on the surface

... I can assure you though, that it’s been used by generations of clock&watch makers, and silversmiths

MichaelG.

I mostly use 0.3 binding wire, but sometimes use 025. The wire is black 'cos it's been allowed to oxidise, and the solder doesn't like to stick to it. I wind 2 coils around the part and then twist the ends together whilst pulling. I generally start twisting and pulling with my fingers, then switch to using pliers up close to the work so as to pull the wire really tight.

Thanks for further info Michael and Gary - I'll have a go with binding.

I wasn't really doubting the wisdom of the advice, just surprised. Now I know about I can envisage several situations where this technique could be useful.

Thanks again, Robin.

Oh, I forgot to mention that, because the wire is thin, if the flame is directed on parts of it not touching the brass it can heat up very quickly and melt. Just avoid directing the flame on wire that's 'out in space' and not touching the work piece. Its all about flame control.