Brandon's point is excellent. There was an interesting suggestion in an
1891 column in "The Blacksmith and the Wheelwright". If you are drilling a
hole in a plough and the metal is too hard for the drill to bite you can put
a small piece of sulfur on the area to be drilled and heat it from the
backside, "until it is cherry red. When cooled the metal will drill
easily." You don't even need to melt the metal for the sulfur contaminent
to diffuse through it.
You can easily check if base metal cleanliness is the problem by practicing
on some clean (non-truck) metal.
Eric is right. Clean is what you want for ANY welding. MIG is a lot more
forgiving though. You are welding a lot faster when doing short-circuit MIG
and there is less time for any contaminents to diffuse. The E70S-6 that is
typically recommended for sheet metal MIG is alloyed to make it tolerant of
some rust and contamination.
----- Original Message -----
From: "Brandon Dixon" <dixon@cs.ua.edu>
To: <shop-talk@autox.team.net>
Sent: Thursday, July 27, 2000 10:49 AM
Subject: RE: Question about TIG
> It is quite possible to
> get contamination of the weld pool from the BACK side of the metal. Any
oil
> or grease or undercoat, etc back there can mess things up big time.
>
> Brandon Dixon
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