Copper Brazing Experiment

[Curtis]

Copper Brazing... never knew it existed until Jerry Huddleston recently recommended it for parts that will be eventually color cased.  He later changed his recommendation for that particular application to pure silver, however the idea stuck in my head and was put on a mental shelf for future reference.

Jerry recommended using an .002 copper shim.  The other day I was discarding an ancient computer hard drive (I am a computer nerd by trade) and noticed it had a seal of copper foil wrapped around it.  A light went on in my head - thin copper stock!! I pealed off as much of it as I could and saved it for later.  After cleaning off some sticky adhesive residue, it miked about .003 or less.  I just happened to have a rear sight that I wanted to make taller and decided it would make a great experiment to see if I could do some copper brazing.  If I decide to use the sight it will be charcoal blued.   I may well be pushing the temperature range for silver solder, but will be safely below copper, silver or brass melting temps.

Here is a somewhat blurry photo of the salvaged copper foil:



This is what I used for flux.  I have had good luck using borax when brazing with brass scraps, as well as a combination of borax and My-T-Flux for brass and pure silver.  More on that in another post later...



I floated the steel parts to be joined on a mill file, then painted a coat of MY-T-Flux on the steel surfaces and both sides of the cleaned up copper foil.



Sandwiched the copper and clamped with an old C clamp.  I used the nail in top of the sight to allow more surface area to be exposed to the torch flame, as well as to provided clearance of the C-clamp.



Sprinkled on some borax just in case, instead of shaking a WOOWOO stick.  Thank you Mike Brooks.  



Hit it with a  propane and a MAPP torch at the same time.  Move the torches around for even heat and wait for the copper to melt:





Cooling.





After cleanup of the slag and filling down the oversize new base, the line is visible but doesn't look bad.  It may show with some finish treatments but I think with a charcoal blue it will all but disappear.  Now I have to decide if I can file up the now taller sight enough to make it esthetically pleasing enough to use.  The copper brazed joint is quite strong regardless!  I think some of the copper must have vaporized, as I found copper traces in several odd places including under the nail.





Thanks for looking.  And thanks to Jerry Huddleston for the idea!

Curtis

[Old Ford2]

Great information!
Thank you for your time and effort.
Fred

[Mark Elliott]

I braze exactly the same way using brass shim stock.

[davec2]

Curtis,

Great post.  In the rocket business we braze all sorts of things together with a myriad of alloys that go liquidus at various temperatures.  We do use braze alloys in the form of sheet, wire, paste, etc.  Often, for situations like this, instead of copper sheet, we electroplate copper to one or both surfaces and then braze.  To change the alloy, and thus the melting point, we sometimes plate one side with copper and the other with gold or nickel or both.

[jerrywh]

  I first used this copper brazing many years ago to braze the pan and bolster on a flintlock plate. It made it possible to case harden the lock plate later.  Thanks js to Curtis for illustrating the process.  Dave. If your using plating to do this it is hard for me to imagine the fits that you have to obtain. I do plating but I don't think I could ever get a fit that close.
 Would it be possible to get a fusion by using gold and mercury at low temp that woks on the order of amalgamation?
   

[WadePatton]

That's what i learned to call "hearth brazing".    I thought you were joining copper.   Fine work, thanks for making the pictorial.   

[T.C.Albert]

I believe iron parts on southern mountain guns are often copper brazed as well.
tc

[Curtis]

Thanks for the comments guys. Dave, the tidbit about electroplating parts to braze together is very interesting.  Not certain floating the material over a file would be precise enough, with me doing it anyways!  You must get to work with some really cool stuff!

Mark, I haven't tried using brass shim stock yet, but I have had good luck using brass filings or small scrap.  It will draw into a fluxed joint like solder.

Jerry, I may be building some lock plates in the near future, playing with things like this is great practice for those bigger projects.  I will probably use some of that pure silver you sent me, but sometimes it is fun to fiddle around with salvage materials.  Used some of the silver on a trigger guard the other day, I will post some photos in the future.

TC, that is some great information, thanks!

Curtis