Chris,
I use one of those automatic darking helments. "Best thing since
buttermilk" as the saying goes. With a regular helment, I mostly wound up
welding
in the wrong place. With the automatic lense I can see where I am starting.
In any case, the lense has some filtering effect for the very short time that
it takes for the lense to go dark. Today I forgot to turn the helment on,
(Push just above the upper center of the lense, it goes black then clears up)
and my first spot weld with a mig was a little bright. (There is less filtering
with the lense powered down). One problem I sometimes have when welding in
a very cramped upside down position: The photo cell in the upper center of
the lense
can be blocked by obstructions, and the lense does not darken.
Speaking of warping and welding patches. I am presently repairing
an Alpine
with considerable rust holes. I have an air operated flanging tool that
works very easy, however the Alpine and Tiger Sheet metal is slightly thicker
than the step of the offset flange that is produced. The patch is therefore
below the
surface of the body panel. I therefore decided to do butt welds. With a lot of
work I got my patch to fit with less than 1/64" gap all around and properly
curved.
Using my Mig (with 30 wire and pure argon) I put 1/8" to 3/16" spots around
the patch. I waited for cooling before going to the next spot weld. Finally
I had spots every 1/8" or so around the patch, and no warping. However, I still
needed to grind the weld down flush with the sheet metal. Using a 4" angle
grinder
(Dewalt) I ground down my welds. I then set back, very happy with my work, when
all of a sudden the fender went pop and had a huge warp in it. Apparently
the heat from
grinding contributed to the problem. Thankfully due to a huge rust hole that
was not yet repaired I was able to reach inside with a body anvail and useing a
body hammer I banged on the ground down welds and the fender popped put again.
On Wire Size: 30 feeds much better than 24. A big spool of wire
feeds much much better than the little 4" spools. In-consistant wire feed
is a major problem in trying to get a consistent weld. I use PAM cooking
spray on the tip and gas lense to keep metal from sticking. Seems to work
as well as the $$ spray from the welding shop. If you slow down the wire feed
too much ( as needed for thin metal) you start "spraying" the weld and it is
likely
that the wire will get stuck in the tip. After the wire has been stuck in the
tip, you might as well replace the tip, as it seldom feeds the wire properly
after that. Use plires to tighten the new tip as finger tight tips do not
transfer heat away from the tip fast enough and the new tip will shortly
stick to the wire again.
After welding a spot use a SS wire brush to clean any brown crap that
shows up around the weld before you attempt to weld near by. The brown or black
crap apparently is due to unclean metal, either the wire, sheet metal or the
PAM.
SS Brushes, about the size of a large toothbrush are available from welding
supply places for a buck or two. I buy them 6 at a time. The brushes are also
handy to remove the undercoating, paint and primer when you heat the area with
a propane torch.
The true key to good welding is to start with CLEAM metal. All
paint, oil,
wax and rust must be removed prior to attempting to weld with a MIG on thin
sheet
metal. If you have 1/4" plate or better to weld than with a stick welder
you can sort of get away with a bit of surface rust. Even for big stuff, clean
metal makes for a much better welding job.
For TIG welding I have read that the metal should be cleaned with
acatone or similar solvent before attempting to TIG weld. I have a TIG, but
the rectifiers failed and I can't seem to find replacements. I believe that
the 5000+ V RF generator caused the 200 AMP rectifiers to fail due to back EMF.
I can not find any rectifiers that can handle the reverse voltage generated
by the
RF box. Added a low pass filter in the line, but the rectifiers still failed.
At 01:18 AM 1/2/2002 -0800, you wrote:
>Punsfluckett, Throttlebottom, Snead and Purvey have advised me to disavow any
>recommendation of welding techniques not approved by OSHA, whoever they are.
> I did want to note that I am very leary of eye exposure in welding.
>Someone here spoke of using a '9' lens for .023 wire, which does make it
>easier, but I'd still never go less than '10'. My helmet is modified with
>leather duct taped to the bottom and side edges so that I CAN safely look away
>(I still close my eyes) without closing the visor, but still only for little
>tap bursts.
> I was tempted by the automatic lenses, but, the 'window' of vulnerability
>before they shade is (if I remember correctly) 1/100th of a sec. That means
>in essence that for every 100 welds (not a lot with a rusty or wrecked car)
>you've looked directly into the arc unshielded for a full second. Not good.
>And that's if you believe it's really 1/100th of a second.
> I don't understand, with all the wireless technology around, why someone
>hasn't produced something that would key off the trigger and shade 1/100th
>BEFORE the arc started. Now that I'd buy.
>
> Chris Hill
James Barrett Tiger II 351C and others
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