WORKSHOP: SILVER SOLDER

Here’s Steve ‘Scoop’ Cooper with your workshop guide to silver soldering tinware.

Scoop tells us what’s hot.

Before plastic became the material of choice with which to clothe motorcycles, steel was the default substrate. Used for guards, headlamp shells, side-panels and the like, it was either painted of plated. If you’re having panels painted then there’s an expectation the guy painting the stuff will sort out your

dinks and knocks as part of the process, after all it is what they do. Yet when it comes to chrome plating not every plater is keen to fix damage to guards, headlight rims and the like. A fair number simply don’t want the hassle of repairing sheet metal items that are often a real faff to sort out, and if they can fix your items, chances are it’ll cost big time. One option is to get the parts stripped of chrome then find a-man-that-can, aka a decent, capable, sheet metal-smith… which is where we find ourselves this month. Having re-homed yet another small capacity Yamaha twin, I found myself in need of guards. Tinware for AS3S is rare at best, but DK Spares had some alternatives that would fit but needed a fair amount of TLC. Once they were stripped of chrome they went to

my mate Iain’s workshop. A wizard with sheet metal, he straightened the badly twisted front blade and reworked the rear so I could mount a UK tail light. All good so far, but the guards still had marks that would show up if simply covered with chrome. As Iain has yet to invest in brazing facilities, another remedy was needed. One option would be to heavily copper plate them beforehand, but this adds serious costs to the project – think £50-60 per guard. Being essentially tight by nature this left me pondering whether it was possible to take out the worst of the blemishes myself. Lead puddling would work, but it makes the plater’s job much harder as he cannot easily polish the soft body solder used.

So would silver solder be viable? My plater reckons it should be fine and especially so if I overload the damaged areas; this would allow him to linish and polish sympathetically. On the basis that I’ve not used silver since I was 14 it looks, potentially, like it’s another school day to me!

And that’s about it for silver soldering a pair of 1970s mudguards. The end result doesn’t have to look pretty, it simply needs to have a surface the chrome plater can linish and polish down to the same level as the base steel. Having handed these over to my local chrome king, I’m told they look better than many of the bodge jobs that he gets handed. In an ideal world I’d be showing CMM’S readers the finished items but, as everyone knows, chrome platers have long waiting times so we’ll simply have to be patient: fingers crossed etc., eh?

3 Typical issues that warrant silver solder intervention. 1/ The area above the central brace shows spot welds and impact damage causing a depression. 2/ More spot welds and evidence of frontal damage via splits. 3/ A welded plate over an unneeded hole has left some large depressions to be filled.

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4/ Before tackling the guards it’s prudent to have a look-see and get a feel for silver solder, especially if you’ve not used it before. Essentially, if you can DIY solder copper water pipe you can silver solder. It just takes longer, requires more heat and produces different fumes/residues. Have a test run on a piece of scrap steel to get a feel for how and when the silver solder melts and flows. Better to find out here than on some irreplaceable panel.

5 5/ The flux is best applied as a paste made up with water in a non-metallic container to a consistency somewhere between single cream and yoghurt. Getting the flux to the correct texture ensures it stays where it’s put.

9 8/ When it’s fully liquefied the silver solder is remarkably fluid. If the workpiece can’t be angled to retain the molten metal then some lateral thought may help. 9/ When the defects have been filled the residual flux has be washed off or corrosion will set it. The workpiece must be cool. If not, thermal shock may occur, partially breaking the bond between the steel and the silver solder. 10/ A cursory wash isn’t good enough: all that green, brown and black goop needs to be removed. Once it’s clean, dry the metal off and store in a warm place.

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7 6/ Heat is applied and the water boils off leaving the flux in place, which gradually melts. From here the silver solder is applied and the aim is for it to melt and drop it into place over the deformed areas. 7/ Careful and controlled application of flame sees the solder melt and flow partially filling the depression. More solder can now be added as required.

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