Subject: What to look for in A MIG

From: [email-masked] (Allan Hill)
Date: Thu, 11 Aug 1994 02:18:33 GMT

I about to but a MIG welder for doing work with sheet metal and other general 
purpose welding.

I used plenty of arc welders - so I know about amps - small stuff low amps - 
the thicker the material - the more amps - a bit rough but it works for me.

So the bigger the amp rating of an arc welder the bigger the welder !

Whats the go when it comes to MIGs - I have heard people talk of duty cycle as 
well as amp ratings ?

What do I need to look at to compare two MIG welders ???

any help appreciated

thanks in advance

Allan Hill
  email: [email-masked]

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From: [email-masked] (Tim Kirby)
Date: 11 Aug 94 14:36:15 CDT

Allan Hill ([email-masked]) wrote:
: So the bigger the amp rating of an arc welder the bigger the welder !
: Whats the go when it comes to MIGs - I have heard people talk of duty cycle
: as well as amp ratings ?

In the end, you are creating a large spark and using that to melt the target
item (one electrode) and the filler (the other electrode). Functionally the
same process except the MIG electrode is much longer than a buzz stick :)

Duty cycle is relevant to any electric welding device. It is an indication of
how long you can run the box before having to let it cool down at a particular
current rating. The higher the number (percentage) the longer you can keep
going, e.g. a 100% duty cycle at 80 amps means you can keep going as fast as
you can with a welding current of 80 amps. A duty cycle of 20% at 80 amps
would mean for every minute of welding you need to allow a further 4 minutes
of cooling/recovery.

It probably gets more visibility with MIG than arc because you *have* to stop
when you run out of rod whereas the wire feed just keeps on feeding.

There is quite a bit of welding information in the FAQ, it is recommended
reading...

Tim
--
Tim Kirby _________ Cray Research Inc., Eagan, MN, USA __________ [email-masked]
Software Division              System Support                +1-(612)-683-5390
__________________________ Consider it disclaimed ____________________________
If all else fails, Immortality may always be assured by spectacular error(JKG)

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From: [email-masked] (Gordon W J Sorensen)
Date: Thu, 11 Aug 1994 23:56:15 GMT

: I about to but a MIG welder for doing work with sheet metal and other general 
: purpose welding.

: I used plenty of arc welders - so I know about amps - small stuff low amps - 
: the thicker the material - the more amps - a bit rough but it works for me.

: Whats the go when it comes to MIGs - I have heard people talk of duty cycle as 
: well as amp ratings ?

: What do I need to look at to compare two MIG welders ???

: any help appreciated

: thanks in advance

: Allan Hill
:   email: [email-masked]

Hi Allan,

Besides duty amps and duty cycle, check out the wire feed system.
That in a large part determines how well the MIG machine will
work.  Personally I would not buy one of the cheapies.  I would
stick to the big 4, Miller, Lincoln, Hobart, AirCo/Linde/whatevertheirname,
I bought the Lincoln Arc SP-130T and like it alot. It was $700 with tank
and regulator.

gordon s.

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From: [email-masked] (Dion Hollenbeck)
Date: Sun, 14 Aug 1994 20:05:55 GMT

>>>>> "Allan" == Allan Hill <[email-masked]> writes:

Allan> I about to but a MIG welder for doing work with sheet metal and
Allan> other general purpose welding.

I won't repeat other answers, but a key to what to get is your wish to
weld sheet metal.  Just so happens, I have experience with MIG and
sheet metal.  My perspective will be from that of an owner of a Hobart
handler 120, running with gas shielding and using it to weld car body
thickness sheet metal (I am repairing the rust holes in my wife's
car).

Very important features are:

	Ability to change wire sizes - thin metal needs .024" wire

	Ability to minutely change wire feed speed (this controls
		current along with current dial selector)

Things to watch out for in technique:

	Do not weld on very thin sheet for more than about 1/4" at
		a time.  Longer than that will blow a hole in it.
		Also, any long welding times will tend to make the
		metal curl up in horrible ways.

	Get your wire stickout down to the minimum you can control.
		This lowers current.

	Add all the heat dissipating applicances you can - clamps,
		fans, heavy copper backers, etc. 

Lastly, get yourself and shade 9 glass and a 500 watt halogen bulb.
Put the bulb in a reflector lamp and shine it on the work area from
about 1 foot away.  In this manner, you can leave your helmet down and
go back and forth around the piece you are welding, putting a "stitch"
here and a "stitch" there, and so on.  You must spread out the heating
around the entire piece evenly by tacking it down a little at a time.
The high power light and low density glass will let you just see the
tip of your gun and with the low current settings you will use, the
brightness of the arc will not cause you to see stars.

Don't be disappointed if you do some practice welding and you blow
holes in the sheet metal.  It will work better when it is in some sort
of context which will help to wick away the heat.

I *highly* recommend the Hobart.  It will handle anything from very
thin sheet metal to 3/8" plate.  It can be run with either flux-cored
wire (definitely *not* my choice) or with shielding gas.  No need to
buy a gas solenoid valve either, just get a gas bottle and regulator
and you are all set to go.

-- 
Dion Hollenbeck (619)675-4000x2814     Email: [email-masked]
Staff Software Engineer     Megatek Corporation, San Diego, California