MIG Welding Basics

Metal Shop
#1

For those interested in melting metal to build something, I thought I would offer some rule of thumbs to help out with knowledge around MIG welding and setting up the machine.

This is just just one way to get some voltage and wire feed settings if you dont have any idea where to start.

  • Let’s take 1/8" carbon steel for example:

    1.) 1/8" inch = .125

    2.) one amp per .001" = 125 amps

    3.) if you are using .035" wire, use 1.6 to figure the wire speed for .125 metal.

    4.) 125 x 1.6 = 200 inches per minute.

That gives you a starting point in setting up the machine.

Now, just adjust voltage to get a good smooth bacon frying sound.

(assuming you are using MIG with 75/25 gas)

Hope it helps for those folks new to a MIG.

Also, our Millermatic 252 has Auto-Gun Detect.

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#2

Good share.
The charts can be helpful, too, if it’s been a while, or you’ve forgotten (because some of us are forgetful like that) for “starting points”, too.

image.png1936×1296 1.98 MB

(all covered in the basics class, too, but again, some of us are forgetful, and don’t get to practice like we’d like)

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#3

Good add-in @jast.

I thought I would also add that, and correct me if wrong, but DMS recommends the shielding gas be set at 15 CFH.

#4

Not psi but CFH. Memory serves me right it should be about 20ish. Personally at home I run higher but I have more air movement around me.

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#5

My recollection, without notes handy, and realising I don’t do this often, and have never done it much, is to start off around 17cfh. The googles appear to agree, most recommending 15-20cfh starting point.

example

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#6

also, page 20 of the manual

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#7

@TBJK - thanks for the correction on the CFM. I edited to be precise.

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#8

Also, I think that should be cfH, cubic feet per Hour, as opposed to cfM, cubic feet per minute. For using the gauge it likely doesn’t matter, as you just set it to “17” (or whatever), but when written and conceptually, and when helping us noobies, they’re quite different… :slight_smile:

#9

Yep. At work I deal a lot with CFM, that why I said it instead of CFH. Guess if I’m correcting I should make it right. Lol. I think I need some caffeine.

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#10

Haha … From now on @jast, I am going to send all my technical posts to you prior to publishing, so you may edit it for precision!! … Lol😀

#11

A few other things to know about MIG welding to make better welds.

1.) Get a better ground clamp. Many of the ones today are crap. Probably the least thought about or understood, but it’s probably the Most Important to know. Have you ever fired off a MIG gun and it has a popping sound? It’s due to a bad ground. It’s simple fix, but I’ve seen people trash machines by not having good grounds. The modern clamps stink. The best ground clamps are copper. Copper offers the best conductivity. Expensive, but much better leading to better welds.

2.) Next is Stickout - probably the least understood for new welders. What it really means is the distance from the mig welding tip (the contact tip) to the arc. Not the distance from the nozzle to the arc. If the contact tip is too far recessed into the gas shield, you’ll get monster weld buildup = longer stickout. The contact tip just poking out= shorter stickout = better penetration and smoother welding on thicker metals. (1/8" and above)

3.) Lastly, get an Auto-Darkening Hood. You are able to lay down the gun and put it perfectly on track and just fire it off instead of nodding down the hood and maybe getting off track to start.

Hope these help!

#12

I will add to this. The better your metal is prepped the better it will weld. In other words the grounding location should be ground free of mill scale. Welding location should be too.

Mill scale is a layer of oxide between the atmosphere and the base metal. This is formed from hot rolling the steel & the oxides appears.

The next best is to get either P&O or cold rolled. Pickled and Oiled steel is hot rolled steel that has been stripped chemically of the oxidation, then oiled. The oil needs to be removed before painting or welding.

Cold rolled, I love it but it is more expensive.

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