Bob La Londe wrote:
"Bill" wrote in message
...

On Sat, 14 Oct 2017 01:46:24 -0000 (UTC), bob prohaska wrote:

I just broke a drawer pull on a family heirloom desk. The pull
consists of a cast brass base with a tab sticking out. The tab
is bent down through the ring, holding it flexibly captive. The
tab is about 1/8" wide and half that thick, the ring about 2"
diameter and 1/8" thick at the tab.

The tab broke where it was bent, so the easiest way to line
up the break is to put the ring back where it belongs and
solder the broken tab back in place. If the tab is soldered
with the ring out, then some bending will be needed to put
the ring back. That seems a good way to break the tab again.

If I can find something to coat the ring pull, so the solder
won't wet it, I think there's a decent chance of success. I
don't think lead-tin solder will be strong enough and I can't
think of a reliable anti-wetting coating that will stand up
to silver soldering temperatures. Aluminum foil comes to mind,
and might work for soft solder but I don't think it'd take
the heat needed for silver soldering.

Thanks for reading, and any ideas.

bob prohaska

How about... White Out? Its used in making canister damscus steel. That's
a lot higher temperature than silver solder. Not sure how you would go
about removing it afterwards though. Another option might be graphite spray
lubricant. I use it all the time in lead casting, although the base metal
(aluminum) of the mold does not wet easily to lead anyway.




It seems as if correction fluid might be a pretty good bet. Near as I
can tell the pigment is titanium dioxide, which is a fairly inert
ceramic. It can be applied thick, perhaps it'll resist flux. Shouldn't
be too hard to set up a rehearsal with some scrap brass for a test.

Speaking of setup, holding the parts in position looks rather difficult;
the broken tab is only about 1/8" square. Can anybody suggest some sort
of putty that will resist brazing heat, hold the (very small) parts in
place and not sinter to something indestructible when heated? Maybe
glazier's putty, but that can get rather hard. Fire stop caulking?
modeling clay? Perhaps something made from household chemicals like
talc and water?

Thanks for everyone's ideas!

bob prohaska