Silver soldering (Brazing ?) and Flux

[picclock]

OK my first attempt was only partly successful as after I fluxed the parts I failed to check the gap at the ends of the joint. I just pushed it up hard and clamped it.
I think the flux resisted me : - oops.

However the part I was most concerned about went well with the part heating quickly enough and the solder flowing readily. It all seemed to happen just as the metal is starting to get red from heat, sort of black with a hint of red to come.

The other thing I think I would do is is to have a spare length of solder ready to put on the joint if required.

The clamp doesn't seem to make any difference to the solder flow, as the side with the clamp flowed the same as the side without.

Using the centre punch marks for the central gap worked well, but I had to punch it at an angle to raise enough metal for the 2 thou gap.

The result looks pretty ugly but its enough for me to know that I can move on to make that perfect joint ;D.

Other pictures at

http://s917.photobucket.com/albums/ad19/picclock/Brazing 101/

Thanks to bogs and others for their help with this.

Best Regards

picclock

 

[Blogwitch]

Picclock,

The gaps are definitely too large to begin with, hence the lack of complete fill by capillary action plus also not enough solder to fill up the space that was set up.

People don't automatically know what a 0.002" (0.05mm) gap looks like.

I explain by saying that the correct gap should be the same thickness as a human head hair (hair on other parts of the body vary in their thicknesses), which on average is somewhere around that 0.002" figure. Usually a lot smaller than people imagine what it should look like.

By going any wider than that is actually weakening the joint, as you are relying on the strength in the solder metal itself rather than in the surface area bond that it gives.

Imagine the solder is like superglue, clamp the parts together and you usually get a rather strong joint after it has set, whereas having loads of superglue in there and not clamped, a very weak joint is produced, actually only the strength of dried up superglue.

I'm not criticising your work at all, you are just starting out on a learning cycle and are bound to make mistakes, no one is perfect, and we all make mistakes, despite what some people think of themselves.
Once you find those magical ingredients, and put them together in the correct sequence, everything will fall into place and you will get repeatable, very strong and neat joints all the time.

Then you will say to yourself 'what was all the worrying about?'.

Keep at it, you will get there.


Bogs

 

[Ken I]

I also keep a rod of silver solder in my hand - in case of need.

Pre-flux the rod tip by heating it and dipping it in powdered flux (looks like a small Q-Tip) that way you have flux and solder available to pitch in should it be required.

Ken

 

[picclock]

@ bogs

I measured those gaps with a 0.05mm (2 thou near enough) feeler gauge before clamping so it was OK up until the point I fluxed and clamped it :. The centre gap is definitely correct but the ends moved.

I think I was more concerned with flux burnout and getting the temperature correct, cleaning and all the other things that may go wrong. Setting a 2 thou gap is not too difficult, however holding that gap in two separate pieces is trickier, especially if they are covered in flux.

That's why I made a test piece to familiarise myself with the process and become aware of the pitfalls which may occur.

Best Regards

picclock