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Oh no - More torch questions


#1

I am an all around craftsman who learned to make jewellery using a
torch and a tank of Propane. Now I am teaching myself to work on
larger things and have purchased an Oxy-propane system with a Sol-Gar
torch (Spanish manufacturer) which is slightly bigger than a Little
Torch. The largest head of the torch I would estimage to be
equivalent to the #7 of the Little Torch.

I am building a small box of 1.25 mm copper 6x4x4 cm. Total weight
of the copper is 110 grams.

It is taking about 2 minutes worth of welding to get make a weld.
After about 1 1/2 minutes the flux turns glassy, then the copper
starts to glow red hot, then all of the non-fluxed parts of the box
turn a silvery-black color, then the solder (medium) melts. There
is no fire-scale. The black goes away after a few minutes in the
pickle.

Does this sound right? 2 Minutes seems long to me but I have never
worked on “large” things before, and I want to build things even
larger.

I have read all of the archived messages on Orchid about torches and
I am a bit surprised at the lack of clear specs for the rights size
torch for a job.

Shouldn’t it be possible to say that for a certain size/weight of
metal to be welded what the BTU/temperature required is and hence
which torch can/cannot handle the job?

Why is this issue being debated?

Thanks for any help

Stuart LeVine
Israel


#2

I’m surprised that no one has posted on this question before so I’ll
give it a try now. First of all, copper is more often silver
soldered (brazed) than it is welded. Copper and silver are both very
heat conductive and so the whole piece has to be brought up to
temperature before solder can melt and fuse to the metal. I’m
surprised that you can weld it at all. I’m not familiar with your
torch. An air/gas torch that makes a big soft flame is usually used.
I’m surprised at your comment about no firescale. When I heat copper,
there is usually a black “crust” that flakes off if allowed to air
cool. I quench mine in water before pickling.

Marilyn Smith