TUTORIAL
Basic brazing: Tin can caddy
Metal conducts
heat. Make sure
you’re working on
a heat-proof, non-
flammable surface,
and be careful
what you touch!QUICK TIP
Trying to weld very thin metal is very difficult, and
often results in ‘blowout’, where the power of the arc
or flame is so high that sections of metal melt away
leaving a hole. This is a particular problem when
you’re trying to weld thick metal to thin metal, and
while there are all sorts of techniques to counteract
this, it’s not easy. Brazing doesn’t rely on melting
the metals that you’re joining, so blowout is much
less likely. In fact, if you manage to get blowout, you
were heating the metal far too much. The brazed
joint will be weaker than a welded joint, but that
doesn’t mean it’ll be too weak to do the job.JOINING THIN METAL
Different types of gas burn at different temperatures.
Butane is the coolest, followed by propane, MAPP,
and then acetylene. For smaller projects, you can get
away with using butane or propane torches with thin
(about 1.2 mm) brazing rods. For larger projects, you
will need the extra heat of MAPP or acetylene to get
the joint hot enough to melt the brazing rods. Hotter
isn’t always better, though, and you can completely
melt small projects with an aggressive gas flame.
Remember that when you’re brazing, you’re trying to
melt the filler rod and not the metal that you’re joining.PICKING YOUR GAS
perfect, you can use powdered flux and a brass or
bronze rod to just ‘tack’ around the can in two or
three places. Powdered flux looks like fine, dry sand
and will stick to a hot brazing rod. The easiest way to
use flux powder is to preheat your brazing rod with
the gas torch, and then dip the rod into a jar of the
powder for a second before removing it. You can
then use the flux-coated rod on the joining surfaces,
and re-dip the rod whenever you need more flux. The
instructions in this article assume that you’re using
brass rod and flux powder for the rest of this project,
because it’s the cheapest and easiest way to braze.
The basic technique for brazing is the same as
soldering. You need to heat the metals you’re joining,
and use them to melt the brass filler rod. You’re not
trying to melt the brazing rod with the flame. Start by
using your gas torch to heat up the join between the
two cans. Try to apply the heat evenly all around the
joint at first, and then linger for a few seconds on the
area that you want to melt the brazing rod to get it up
to temperature. Heating all around a joint is good
practice because metal expands when it heats up,
and will distort if it’s heated unevenly. It’s probably
fine with a tin can, but when larger projects cool
down unevenly, the tension created by the distortion
can be strong enough to break the brazed joint.NOT TOO HOT, NOT TOO COLD
Keep the tip of your gas torch pointed at the joint,
and touch your flux-coated brazing rod to the section
you’re heating. The alloy should melt quickly, and
flow into the joint. Push more of the brass rod into
the joint as it melts, moving along to increase the
length of your braze, re-dipping the rod in flux
powder as needed. If the brazing rod seems to just
slump or just sit on top of the joint without melting,
then you haven’t applied enough heat. Either go
slower, use a hotter flame, or use a thinner rod.