From: pvr@wang.com (Peter Reilley)
Subject: Re: MIG Welders... Why not TIG?
Organization: Wang Labs, Lowell MA, USA
Date: Tue, 21 Jul 92 17:51:59 GMT

mdl@phelixsalt (Michael Lynch) writes:

>This TIG attachment sounds interesting.  You say it's an attachment.
>How is it attached?

	There are 3 pieces; a torch, a RF unit, and an inert gas cylinder 
with regulator.   The torch draws the arc from a tungston rod that
is surrounded by a ceramic bushing to confine the gas.   The RF unit
goes between the standard arc welder and the torch.  The gas is fed
to the torch in the normal way.

	My arc welder is AC only and works fine with my TIG setup.

>  When you say you can use any metal rods, I
>assume you mean rods with flux on them, right?

	The inert gas eliminates any need for flux.  The gas excludes
the air so there is no oxidation.   The gas also cools the torch.

>  You have to use two
>hands -- is one for the gas feed?

	One hand to hold the torch and one to hold the welding rod.

>I have an arc welder, and it would sure be nice to be able to weld
>without the coated rods.  I want to know more.  Approximate cost?
>Sources?

	I got mine from Sears.  The RF unit was available seperately
from the torch.   The RF unit was about $150 4 years ago when I
got the system.  The torch and gas regulator was $125 as I 
remember.

	I recommend the RF unit but not the torch.   A TIG or MIG
RF unit is quite a simple device.   It is a air core transformer
with one winding of heavy wire that is connected in series
with the welding cable.   The other winding is of light wire
that is connected in series with a high voltage transformer
and a spark gap.   When operating the high voltage arcs
the gap.   This generates high frequency noise that is coupled
into the welding lead by the air core transformer.   The energy
of the RF is enough to ionize the inert gas.   When the tip
is brought close to the work piece the low welding voltage
will conduct through the ionized inert gas without touching the 
tungston tip to the work piece.

	The Sears torch is a device that you clamp in your
standard arc welding rod holder.  It has a little valve
in it for turning off the gas when not in use.   The regulator 
that they supply is a pressure regulator, and what you
want for TIG or MIG is a flow regulator.   Welding specifications
are given in gas flow rate through the torch tip.   You cannot
relate pressure to flow rate.

    You can tell a flow regulator
from a pressure regulator by its gages.   A flow regulator
has one pressure gage and a tube with a ball bearing that floats 
up and down as the flow changes(I forget the name).   Tha tube
has a markings that indicate flow rates.   A pressure
regulator has two pressure gages.

	I sold the regulator at a flea market and bought a used flow 
regulator that I use.   The torch does not have good heat disipation
properties and is brased together.   Mine over heated and fell apart.
I repaired it and put a heat sink on it which helps.   It is also
not insulated so touching the side of the torch to the work will
cause a short.   For about $100 you can get a professional
TIG torch.   A water cooled one is somewhat more.   If you
buy a professional torch you will need some sort of gas valve.

	Good Luck
-- 
>>>>>>>>>>>> Peter Reilley ..... pvr@wiis.wang.com ..... KA1LAT <<<<<<<<<<<<<
                     Well, that about says it.