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Re: Spot welding vs MIG welding

To: Mark Jurras <jurrasm@genesis.torrco.com>
Subject: Re: Spot welding vs MIG welding
From: "W. R. Gibbons" <gibbons@northpole.med.uvm.edu>
Date: Wed, 10 Jul 1996 10:23:55 -0400 (EDT)
On Wed, 10 Jul 1996, Mark Jurras wrote:

> I have seen a bit of discussion about spot vs MIG welded panels. I am
> no expert on weldong but, spot welds can be done with a MIG. To do this
> drill a small hole (~1/8" or so) in the front panel where it touches
> the rear panel.
> 
> 
>  Front    Rear 
>  Panel    Panel
>       \  /
>        \/
>        ||
>        ||
> Hole >  |
>        ||
>        ||
> 
> Next weld the rear panel to the front panel inside the hole and fill the hole
> 
>  Front    Rear 
>  Panel    Panel
>       \  /
>        \/
>        ||
>        ||
> Weld > @|
>        ||
>        ||
> 
> grind the weld flat and you have what looks and acts like a spot weld.
> 
> Any MIG experts out there that can describe this better than I did?

You described it fine.  I prefer the hole to be larger, 3/16 - 1/4 inch. 
It makes it easier to be sure the back panel is tight against the front
(you can see through the hole), and gives a larger weld area and better
penetration.  You weld around the edge of the hole.  This is sometimes
called a rosette weld or a plug weld. I tend to use a hotter setting on
the welder than I would use if seam welding two sheets, because the
welding only lasts for a few seconds. 

I have a pneumatic tool that is very handy for this.  It is a flanger, 
which presses a flange into a panel so a repair panel can lie flush. The 
other side of the jaw punches 3/16 inch holes for plug welds.
  
   Ray Gibbons  Dept. of Molecular Physiology & Biophysics
                Univ. of Vermont College of Medicine, Burlington, VT
                gibbons@northpole.med.uvm.edu  (802) 656-8910


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