[TheForge] Brass/Bronze brazing question

[Andy Vida]

PlumDon at aol.com wrote:
> 
> A friend has brought over a W and arm that has broken off his weather vane.
> It appears to be brass or bronze and has an obvious large crystaline structure
> evident in the break. The weather vane depicts a carpenter motif with a man
> sawing wood. He would like me to braze it back on.

	You can definitely do this.  If the grain structure is
	that coarse, I'm not sure what would cause it in non-ferrous
	material, but perhaps it is the nature of the alloy or
	maybe the casting chilled at the wrong rate.  
> 
> I'm leery of undertaking this. It looks to me like it was cast and I dont
> know if you can successfuly braze cast bronze...or whatever it is. The piece is
> about 3/16-1/4" thick. I'm inclined to think it would be best to patch it back
> together with a couple pieces of brass on each side and four rivets to hold it
> in place. But I dont really know.

	If the pieces mate well, my suggestion would be to finely
	divide some medium silver solder and join them that way to
	start.  Then do the plates and rivets, and then finally
	solder the whole shebang together with finely divided easy
	solder.  Sweat everything together and when cool, file the
	rivets flush and dress the ends of the plates with a round
	file into an ogee pattern.  The result can be very fine
	and appealing if you keep the joints very tight so that
	little or no silver whows through.  The joint, if done
	right, will outlast the rest of the vane in all likelihood.

	As to the soldering... the finely divided silver is placed
	into the joint with some borax.  Fix the pieces together and
	heat, adding flux to the outer surfaces.  When the silver flows,
	keep at heat for perhaps half a minute to make sure the inner
	portions of the joint flow also.  Pickle the piece in acid to
	remove flux.  File the surfaces very flat, though you can leave
	some fine tooth for added surface area.  Prep the side plates
	to mate VERY closely to the vane.  Drill and rivet tightly.
	Then sweat with the easy solder, or you may even be able to use
	plumbers silver solder, which will be strong enough for this
	application.  File all seams.  If you've done the fitting
	right, you will see no more than a thin line of silver a few
	thousandths of an inch wide, if that.  This joint will be
	very strong.  You can be a little artistic with the plates
	and anyone knowing anything about such work will know that
	a real artist and craftsman affected the repair.
> 
> Any suggestions much appreciated.

	I hope this makes sense.  Sounds mroe complicated than it is.

	Best.

	-Andy