On Jun 10, 6:39*pm, "Artemus" wrote:
Obviously I'm doing something wrong here as my joints are brittle
and don't hold worth squat. *I ground the ends of the blade to about
45 degrees and cleaned the ends with sandpaper. *I put on plenty
of flux and wedged a small piece of silver solder in the scarf joint.
Both ends are held in a jig so nothing moves during the soldering.
The saw blade is 3/16 wide and .025 thick. *I'm using oatey 53013
silver solder. *I'm using a propane torch w/ pencil tip burner.
I've tried heating just till the solder melts & flows, and hotter, up to
the blade turning a cherry red. *Nothing worked.
So what am I doing wrong? *technique? * Wrong solder?
Art

Yep, wrong stuff, as the other posters have said. If you google up
"bandsaw blade brazing jig", you'll get a ton of hits, including how-
to videos. Won't go into the usual rant about calling silver brazing
silver soldering, you've found out the difference. If you want the
right stuff at the welding supply, you ask for "silver brazing
filler", or you'll end up with mostly tin soft solder. The next
question will be what alloy and there you'll have to see what they
have, literally hundreds of alloys and trade names out there, what
I've got available here isn't going to be what anyone else will have
around. You'll need the line sheet for what they carry and decide
what you need from the properties listed.

Used to be HF had a cheap kit including a jig, apparently no longer.
A jig can be made out of a length of aluminum angle and a couple of
bulldog clips. Whack a gap in the center of the piece on one side for
joint clearance, put the untouched side in the vise and use the
bulldog clips to hold the blade ends in position in the gap. You can
scarf the ends by flipping one, placing them on top of each other even-
up and grinding both at the same time. Angles match that way and any
fore-and-aft angular mis-match is compensated for if you grind things
straight. You've got to have things spotless, including the silver
braze itself, degrease with acetone, MEK or the brake cleaner of
choice. For this sort of work, you need almost foil thickness for the
filler, hammer what you get down really thin, sandwich a sliver
between the ends. It was supplied that way in the kits. Flux has to
match, too. The blades are pretty thin, so unless you use some really
high-temp braze, a turbo torch should work. See what the line sheet
says for the alloy, it'll have melting points on it, and choose one
that's lower temp. Air-acetylene or oxy-acetylene will be faster,
probably won't do the job any better and definitely will cost more.
If you really want to go fancy, you could use some stop-off or anti-
flux to keep your after-action filing and cleanup down to a reasonable
amount. I've used it on gun work to keep the filler from wicking all
over a part, won't do a job without it now.

Have read of hammering out a silver dime, using solid borax for a flux
and a kerosene blowtorch for doing the job in a really old book, so
they've been brazing ends together a looong time. A lot longer than
there have been dedicated pushbutton electric welding machines to do
the job.

Stan