Stainless 316 wire rope - solder?

It is possible to solder stainless steel, but I would be surprised if plumbers flux worked very well. I used to use a mix of 25% hydrochloric acid and 75% Bakers Fluid No 1 when soft soldering stainless.

Colin Bignell

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Thanks.

What concentration of HCL do you need? Would brick acid do it?

It's the chlorine that is important and if it really is possible to solder stainless, zinc chloride solution is the usual 'heavy duty' flux.

However: I would have thought there is no point in buying 750kg breaking strain cable and then sticking it together with something about as strong as cheddar. Certainly when I used to try and fashion new nipples on the end of bowden cables to bodge my old bike brakes, they never stayed on v long!

Take it to a yacht chandlers.

Andy

Sorry, I should have said it was concentrated HCL I used, bought from a local chemical supplier. It is, of course, a dangerous chemical and you add the acid slowly to the Baker's fluid, if anyone is not aware of that.

Colin Bignell

That takes me back - bad memories of multiple resolderings of nipples on brake /clutch cables of 50s-60s era Matchless and Norton motorbikes.

You normally splay out the ends of the strands into a hole at the back of the nipple rather larger than that for the cable. So the solder joint isn't just in shear.

Yup, didn't ya just dread that sudden pop and wheelie while you were waiting for the lights and could see the cable going but do nothing about it!

Isn't Bakers Fluid, Zinc dissolved in Hcl making Zinc Cloride ? so you add more acid ? Don

Thanks for that useful info. Saved in my workshop file. Cheers Don

The formulation is a little more complex than that - there are three different Bakers Fluids - but essentially yes. Bakers Fluid No 1 by itself is not aggressive enough for stainless.

The surface of stainless steel is protected by a layer of chromium dioxide and hot HCL is a very effective way to strip chromium plate. So I think that the combination of heat and the extra acid cuts though the surface layer, allowing the solder to bond to the steel underneath, fluxed by the Baker's Fluid.

Colin Bignell

No, not a hope. To soft solder stainless (and esp. 316) you have to use a flux so powerfully evil you'll never get the traces out of a wire rope.

Easiest way is to use silver solder instead. Costs a little more, needs a gas torch and a pinch of a fluoride based flux like Easyflo (try eBay or the model engineering shops for small quantities). 316 loves this and will slurp it up by capillary action, giving a good strong joint.

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "spamlet" saying something like:

You're supposed to fray out the end inside the ferrule and the solder fills it all up, preventing the cable being pulled through.

Still, if you were unaware of this, it's not surprising they failed.

Indeed. I've made lots of cables using that method without a failure. The solder is then under compression rather than shear.

A simpler flux which works very well in conjunction with tin/lead solder is pure phosphoric acid. (It may also work with lead-free solder, but I haven't tried this.) Phosphoric acid, being only a little more viscous than water, can easily be washed out afterwards leaving no corrosive residue. It does of course need to be handled with reasonable care, especially because it can spatter during the soldering.

John

You lot must have been using some pretty light weight clutch springs! Do you really think you are the only ones 'clever' enough to have thought of splaying out cable ends before soldering them!? ( I used to dream of being able to afford a welding/brazing kit...) My BSA 'Thunderbolt' clutch had springs so strong the lever would gradually force my hand open if I tried to hold it in for long (And even then the b...... plates slipped most of the time!). The only way I could bodge nipples for this that worked, was to run the cable through an internally threaded steel tube and bolt them in place (Rather like beefed up wirings in a plug. Actually, come to think of it, you could buy them as emergency nipples and always keep a couple in with your puncture kit and chain splitter...) Did eventually get round to buying a special clutch, but by that time I'd also got a Honda in pieces...

Glad somebody noticed at last. I found it v interesting too. I've always folded and screwed/riveted, stainless up till now: but I do have some (allegedly) stainless welding rods - It's just that I'm rubbish at arc welding anyway!