From: jim@remtech.com (Jim Levie)
Subject: Re: MIG Welders... Why not TIG?
Organization: Remtech Inc.
Date: Tue, 21 Jul 1992 04:17:49 GMT

jws@billy.mlb.semi.harris.com (James W. Swonger) writes:


> TIG (tungsten inert gas) welding provides the benefits of inert-gas-
>shielded arc welding ala MIG but uses a tungsten electrode in the handpiece
>which is not deposited. The tungsten's high temperature strength and its
>resistance to being blown along by the arc current let you work for a while 
>on one electrode. They do wear out and you buy replacements periodically.
>The electrodes are 1/8" dia, 6" long rods and come in boxes of a dozen or
>so.

The TIG torches I've used will take a range of tungsten rod sizes.
There is a collet assembly within the torch that is changed to accept
different sized rods, which are picked based on the welding current
needed. 

> The arc heats a localized area of the workpiece and the filler material
>is worked into the hot spot like with a gas welding setup, only without 
>the problems of flame chemistry, heat spread, etc. and again without flux.

True, flux isn't needed, but for a decent TIG weld the weld zone must
be absolutely clean, bright metal. Any weld zone contamination tends
to contaminate the tungsten electrode and cause an unstable arc or a
bad weld. Since TIG welding requires a filler rod, like gas welding,
greater skill is required of the operator than with MIG welding.
Unlike gas welding you can't pause with a TIG torch as that would
break the arc.

> Somebody had suggested the same thing to me, as a low-budget alternative
>to a MIG welder - a rectifier setup (or a DC box), a TIG torch and a gas
>feed.

Actually DC isn't necessary, you just use up the tungsten faster. An
RF arc starter is an absolute necessity, you can't start the arc by
touching the tungsten to the work. Also I'd consider a water cooled
torch to be essential to get any reasonable life from the tungsten
electrode.

> So tell us more about how your setup works out for you, cost, etc. Sheet
>metal work? Can you braze or is the arc too hot?

Most of the TIG welding I've done on sheet metal (mainly stainless and
aluminum, .020-.090") required a backing heat sink to keep from
blowing out the weld or causing unacceptable heat distortion. A TIG
torch puts out a LOT of heat, even at low amperage and your
torch/filler control had better be nearly perfect. A MIG setup is much
easier to use, and I find it does a better job on steel.  TIG is best
reserved for hard to weld materials like stainless and aluminum or
when weld quality is of the highest importance.

>-- 
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-- 
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 Jim Levie                                  email: jim@chimera.remtech.com
 REMTECH Inc  Huntsville, Al                (or)  ...uunet!remtech!chimera!jim
 The opinions expressed above are just that     Ph.     (205) 536-8581
Newsgroups: alt.autos.antique