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Backlash
 
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Default Home Brew Spot Welder

Eric, The capacitive discharge unit is a factory built unit. I drug it out
of a storage barn at work and put it into action about 10 years ago. It uses
vacuum tube technology to load and discharge a bank of caps through the
tips. I can get the model number and such if you want, but I'm pretty sure
it's now considered obsolete.
I had a similar experience to yours. I needed to externally swage some
..065 stainless steel tubing with a .002 wall thickness down to .035
thousandths for a length of 1/8". Torrington Swager Co no-quoted the tooling
and said they wouldn't touch the job. I took two small blocks of tool steel,
clamped them in the mill vise, and drilled a hole on the parting line of the
blocks. Deburred with a beadblaster, hardened them, polished the bore, and
installed them and went to swaging. They are theoretically supposed to have
all kinds of reliefs ground into these type blocks to make them work, but
these have been turning out thousands of parts a year for about 10 years.
Reality versus perception, I guess.

RJ

--
"You're just jealous because the voices are talking to me, instead of you."


"Eric R Snow" wrote in message
...
On Fri, 23 Apr 2004 08:01:43 -0400, "Backlash"
wrote:

Spotwelders can actually be pretty simple. An appropriate transformer,
timing device, relay to control transformer primary supply, and

mechanical
clamping of the tips are what are required. We have several shop built
spotwelders at work to weld smaller parts. I have a 15 KVA commercial

unit
at home. To weld sheet metal body parts, I think you'll need transformer
ratings of about 5 to 15 KVA. The electrical expert types will have to be
the ones to determine this. I use 15 KVA units to weld 1/16" steel

tubings
telescoped together on a setting of 3 of an available 5 on the range
selector of a factory built unit. Water cooled tips are used for

production
work. A capacitive discharge unit is what I use to spotweld brass to

bronze,
and brass to stainless. Spotwelding basically is a process of mechanical
clamping pressure at the tips, electrical power applied through the tips,
holding time for this power, then release of clamping. All of these
variables are adjusted for weld quality of the "nugget". Special coppers

are
required, and tip diameter is important. A company called New Southern
Resistance Welding is where I get my basic supplies. Miller makes a

handheld
unit for body panels. Maybe you could copy it's design. Hope this helps

you
a little.

RJ

A couple years ago I made some screens for a customer that consisted
of a brass frame with brass chicken wire. The frame was silver
soldered at the corners and the screen was soft soldered to the frame.
I wanted to spot weld the screen but Miller said it was impossible.
Now, I read your post about doing something similar. Did you build the
capacitive discharge unit yourself? If so, would you supply
schematics?
Thank You,
Eric R Snow