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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work.

Home Brew Spot Welder



 
 
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  #1  
Old April 21st 04, 09:31 PM
Howard Eisenhauer
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Default Home Brew Spot Welder

Anybody here ever built your own spot welder? I've got some major
re-assembly work coming up on my jeep tub & I've been thinking it
might be easier/faster to do real spot welds instead of the "drill
hole/mig weld plug/grind down" route. I've found a few references on
google to plans for units using re-wound microwave oven transformers,
intended for use on small projects such as model gas turbines, but
there isn't enough detail to convince me they'd work on heavier sheet
metal.

So, if you have any experience with something like this or know of any
on-line resources that google (Gasp!) doesn't know about I'd
appreaciate hearing from you.

Thanks,

Howard.
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  #2  
Old April 23rd 04, 02:01 PM
Backlash
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Default Home Brew Spot Welder

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

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


"Howard Eisenhauer" wrote in message
...
Anybody here ever built your own spot welder? I've got some major
re-assembly work coming up on my jeep tub & I've been thinking it
might be easier/faster to do real spot welds instead of the "drill
hole/mig weld plug/grind down" route. I've found a few references on
google to plans for units using re-wound microwave oven transformers,
intended for use on small projects such as model gas turbines, but
there isn't enough detail to convince me they'd work on heavier sheet
metal.

So, if you have any experience with something like this or know of any
on-line resources that google (Gasp!) doesn't know about I'd
appreaciate hearing from you.

Thanks,

Howard.



  #3  
Old April 23rd 04, 04:27 PM
Eric R Snow
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Posts: n/a
Default Home Brew Spot Welder

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
  #4  
Old April 24th 04, 01:18 PM
Backlash
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Posts: n/a
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



  #5  
Old April 24th 04, 05:28 PM
Eric R Snow
external usenet poster
 
Posts: n/a
Default Home Brew Spot Welder

On Sat, 24 Apr 2004 07:18:14 -0400, "Backlash"
wrote:

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

Well, thanks anyway. Guess I'll look into this type of spot welder and
see if I can build one.
ERS
  #6  
Old April 24th 04, 07:01 PM
jk
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Posts: n/a
Default Home Brew Spot Welder

Eric R Snow wrote:

RJ

Well, thanks anyway. Guess I'll look into this type of spot welder and
see if I can build one.
ERS

Jewlers use little versions for welding posts on to ear ring bodies
jk
  #7  
Old April 24th 04, 10:13 PM
Coresa
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Posts: n/a
Default Home Brew Spot Welder

Eric,

You may give this a try: http://www.5bears.com/theshop.htm

This chap has some very nifty projects.

Cheers,
Norman
  #8  
Old April 25th 04, 12:53 AM
JR North
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Posts: n/a
Default Home Brew Spot Welder

http://www.metalworking.com/dropbox/...retired_files/
See welder00.txt and the associated jpgs.
JR
Dweller in the cellar
Howard Eisenhauer wrote:

Anybody here ever built your own spot welder? I've got some major
re-assembly work coming up on my jeep tub & I've been thinking it
might be easier/faster to do real spot welds instead of the "drill
hole/mig weld plug/grind down" route. I've found a few references on
google to plans for units using re-wound microwave oven transformers,
intended for use on small projects such as model gas turbines, but
there isn't enough detail to convince me they'd work on heavier sheet
metal.

So, if you have any experience with something like this or know of any
on-line resources that google (Gasp!) doesn't know about I'd
appreaciate hearing from you.

Thanks,

Howard.


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  #9  
Old April 25th 04, 04:51 AM
richard
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Default Home Brew Spot Welder

JR North wrote in message news:
Anybody here ever built your own spot welder? I've got some major
re-assembly work coming up on my jeep tub & I've been thinking it


I fooled around with microwave transformers, i made it work, but not
well enough to do body work, worked quite well on stainless steel
though.

while i was fooling around some one called around and when he saw what
i was doing offered me an old handheld spot welder. It's magic, not at
all fancy no timer or ajustment. you just clamp it and give the
trigger a squeeze, you hear a click and the weld is done...

the bloke I got it off used to use long arms in it and was able to do
all the spot welds in a mini body shell, i gather he needed a helper
to hold it as the whole thing got a bit awkward to use....

I would buy one secondhand and sell it when your finished, probably
won't cost
you anything in the long run and it should work fine.

--
richard
  #10  
Old April 25th 04, 05:24 AM
Howard Eisenhauer
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Posts: n/a
Default Home Brew Spot Welder

Thanks Jason, a couple of questions:

How did you determine the number of secondary windings required?

Will your unit handle 18 gu. steel without suffering a meltdown?

Did you try differnt combinations of series/parrallel on the
transformer windings to find what works best?

Thanks again,

Howard.



On Sat, 24 Apr 2004 15:53:55 -0700, JR North
wrote:

http://www.metalworking.com/dropbox/...retired_files/
See welder00.txt and the associated jpgs.
JR
Dweller in the cellar
Howard Eisenhauer wrote:

Anybody here ever built your own spot welder? I've got some major
re-assembly work coming up on my jeep tub & I've been thinking it
might be easier/faster to do real spot welds instead of the "drill
hole/mig weld plug/grind down" route. I've found a few references on
google to plans for units using re-wound microwave oven transformers,
intended for use on small projects such as model gas turbines, but
there isn't enough detail to convince me they'd work on heavier sheet
metal.

So, if you have any experience with something like this or know of any
on-line resources that google (Gasp!) doesn't know about I'd
appreaciate hearing from you.

Thanks,

Howard.


 




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