I've been taught when soldering hollow forms you should always have a hole in your piece to let the heat escape
This is a statement I have heard from thousands of people , schools,
teachers etc… and is true based on the method of soldering you are
using. My reason for stating this about the " method" is that there
are ways to achieve this without drilling holes.
In One of my past existences , I had developed a very large , volume
electroforming systems for a company that I was managing. It was
used to produce statuary and baby rattles for companies such as
Tiffany and others. Once we had the electroforming process down pat,
We , in many cases had to solder the items closed… In a few cases,
it was not just a pin hole… one particular case we had to solder a
sheet of silver about 2" by 1 1/2 " that was cut to correspond to
the shape of the bottom of the item. another case was were we had to
solder 2 stamped halves of a large diameter Baby rattle perfectly…
In all cases, there could be no pin hole and no pitting in the
seams.
The way I achieved this was as follows:
I built a rotating jig on top of a “lazy susan”… this is a laymans
term for a small rotating table … a simple bearing or rotating
device underneath a high temperature soldering board.
The jig was a “U” shapped device ( make the U upside down from how
it looks here) with a rod going through the center of the top of the
U. This rod also had an adjustable spring on it so that pressure was
applied downwards towards the table. The whole thing was bolted
through the heavy insulation board of the rotating device.The spring
on the rod is important as this is what will allow the pressure to
escape from the piece being soldered and keep the part aligned when
the pressure is released. You can accomplish the same thing without a
spring by substituting a weight that fits on top of the rod. You
would have to use different weights in this case depending on the
job you are soldering. this is why I developed the adjustable spring
tensioner instead.
At the end of the rod, I had screwed on a piece of high temperature
insulation board that had been gound by hand to conform to the curve
of the item to be soldered. On the bottom plate, I had another piece
of insulation ground to conform to the bottom of the piece.
Now, What we did was take the 2 halves to be soldered together, and
flux both sides. Then we put them together and set the spring tension
so that it would just hold the item closed. Flux the outside seam.
Now, we used a large torch ) natural Gas and air… and heated the
whole item up to soldering temperature and turmed the piece while
doing so …so that the item was at an even temperature all the way
around. when the item arrived at soldering temperature, you could see
the 2 halves pop up for a split second and snap back together. This
just released the heated air on the inside . Now, I started to touch
the solder to the area to be soldering seam, soon the solder would
flow completely around the entire seam. I would then remove the heat
and allow it to sufficiently cool before dunking the item in water.
If you watched the item as you put it in hot water after it was
cold, you could see tiny airbubbles seeping out on the ones that had
tiny pinholes. This was very rare( about 1 piece in 50) and was
usually caused by not having enough flux in an area …so the solder
did not flow in that area. These pieces were fluxed and heated back
up … when they got hot enough, steam would escape through the pin
hole… wait until it stops… touch some flux to the area again and
it would the solder shut.
Using this method, we produced over 50,000 of this item. All of them
passed pressure tests as these were baby rattles that sold for over
$250/piece. The item is still being produced at this time. Literally
hundreds of different items in large volume were then produced
because the technique had been mastered by the solderers who worked
for me at that time. It was not easy to train a new solder person as
the concept did not come easily to them . You had to wait for the
air to escape before beginning to solder, so you had to pay close
attention.
Now, I must say that this was attempted by a few solderers who did
not use the jig and their failure rate was 50 % or more . They felt
that it was faster to simply not use the jig. I had to prove to
these people that it worked as they were a lot older than I was at
the time and they had been production solderers for at least 15
years…
So, If you want to solder hollow pieces of anysize, and you will be
doing this a lot, build , or have a person build you a jig of this
nature. It should not cost much and will save you tons of time (
which is money) I don’t build these jigs at this point in time
because I’m just to busy , but anyone can use this idea and have one
made .
Daniel Grandi
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