DIY Solder Paste and a Ball Mill

[Aaron Moss]

I do a lot of brazing and soldering and I was hoping to do a little DIY solder/brazing paste.

I was thinking about getting a harbor freight rock tumbler, filling it with marbles and brazing rod and letting it run for a week, mix the resulting powdered metal with some white brazing flux and give it a try.  Not for everything, but I think it has a place.  I primary run Harris 35 silver, so it's good stuff, might do it with the 56 for improved flow ability.

For the solder, I was going to mix it with Oatly tinning flux, different solder of course, but it has body to keep it in suspension.  Harris Stay clean flux is good, but it's a liquid and nothing will suspend.

If you have any thoughts, ideas, or suggestions I would really appreciate them.

Thanks

Aaron

[George N. M.]

I don't know if it will have any effect on the finished product but I think that the finished slurry from your polisher/ball mill will have lots of silica in it from erosion of the glass marbles being used as mill balls.  The brazing rods will erode them as they erode the brazing rods.

Generally, you want your grinding medium in a tumbler or rod/ball mill to be harder than what is being ground.  Bronze and glass are pretty close with the bronze possibly having the edge.  That is not to say that you can't grind harder material, quartz is regularly ground in mining ball mills.  Quartz is harder than the steel mill balls but is much more brittle. 

I have never heard of metal being ground in a ball mill.  The malleable nature of metal would make it resistant to being crushed and ground up.  I think you would end up with a lot of odd shaped nuggets of bronze and ground to nearly nothing glass marbles.  

You might try using ball bearings as mill balls (harder than glass marbles), dry the slurry, and then remove the steel dust magnetically if the bronze brazing rods were actually reduced to a powder which, to me, seems improbable.  It still seems to me to be a lot of effort but that is up to you.

"By hammer and hand all arts do stand."

[Steve Sells]

you can just buy powdered borax ya know

[Aaron Moss]

George,

You're right about the balls, can use a magnet to pull out the steel, keep the brazing powder clean.  I know they do aluminum, hence powdered aluminum, I might pre-grind with a rotary rasp into tiny flakes and either use that or use that as a ball mill starting point.  I know they do make brazing paste, but it's a different application that what I use, and as far as I can tell Harris doesn't offer it.  Still kicking around options, it's one of those things where it's not an easy solution.

In researching this, apparently they powder a lot of types of metal, like titanium and similar, they use it for special types of 3d printers to make aerospace parts.  So it's not impossible, just difficult.

Steve,  We're not talking about the flux, we're talking about the metal that will go into the flux.  I'm hoping to figure out how to powder Harris 35 silver brazing rod, a few oz of it.

Thanks

Aaron

 

[George N. M.]

Aaron:  I think the best way to powder metal would be with some sort of abrasive or tearing action rather than a crushing action.  Yes, there are powdered metals but I don't know how they are produced industrially.  I suspect that is some sort of cutting or tearing process with something harder than the metal.  The problem would be separating two non-magnetic materials.  You might have to use some sort of gravity or flotation separation to sort by differential density.

As an old geologist I tend to think of the ways that metals are extracted in ore processing.

"By hammer and hand all arts do stand."

[Chris Williams]

George, you have some familiarity with one method of powder production based on your background, even if you didn't even realize it. Direct ore reduction to sponge, followed by crushing, is one method. Separation is still required in this method. 

https://www.mpif.org/IntrotoPM/MakingMetalPowder.aspx#:~:text=There are four main processes,atomization%2C electrolysis%2C and chemical.

[ThomasPowers]

I remember a Medieval Indian technique for smelting zinc  from ore into metal---it's a problem as the smelting temperature is above the vaporization/re-combine with O2 temp.  They got around this by smelting it in alembics with the nozzles sticking into an oxygen deprived cooler space.  The Zinc vapour could then cool down and form a very fine zinc metal powder that could then be collected and melted into ingots.

[Frosty]

 Seeing as we're brainstorming methods of producing fine metal powders in the home shop, how about "sputtering"? No not the complete process, just the vaporization in an inert atmosphere or vacuum. The brazing (or whatever) rod is melted by an arc and is negatively charged and is blown away from the points with a jet of inert gas. The positively charged target being a your chosen flux in a saturated solution. It chills the vaporized metal AND coats it with flux. Filter the fluid and viola!

Hmmm?

Frosty The Lucky.