Bad Mig Tacks: Craters

[longyard]

I'm doing a good bit of Mig work with sheet metal lately, something I've rarely done before. However, I'm having problems creating good tacks. My tacks are gray and form little craters. When I grind the tack down to level, it takes on a "donut" shape.

The last time I tack welded sheet metal was about 20 years ago, and if my memory is correct my tacks were blue-ish, and domed.

I'm using a good Lincoln 180T 220 volt unit with mix gas, and .025 ER70S wire.

Any thoughts?

[Marty Comstock]

Sounds like not enough shielding gas. Liner could be dirty, or your gas diffuser could be plugged with yards of nozzle dip and spatter.

Or I could be wrong :-)

[longyard]

Thanks Marty. I'm also noticing brown soot around each tack. I've got my gas cranked up to 20, but maybe I have a liner issue as you suggested.

[Marty Comstock]

holding the nozzle to your ear (not in your ear unless you want an unpleasant poke of wire) you should hear and feel the *piff* of gas as you pull the trigger.

Scientific, I know.

[longyard]

I'll test it in the morning. BTW, I just changed the liner back from the one I used for flux-core welding.

[longyard]

Marty,
I couldn't wait for the morning, so went out to the shop and tested the welder...NO gas flow! Huh? So I've got to find the blockage in the morning. Thanks for the tip.

[Maxakarudy]

Bill, you should check the gas flow at the nozzle with a flow meter like this, they are cheap, remember to disconnect the wire feed if you testing on a mig
flow meter.jpg

[Marty Comstock]

I want one! Do you have a trade name, or supplier you could share?

I suppose I could Google search it, but I am feeling lazy at the moment

[RockHillWill]

I am interested in one as well.

[Marty Comstock]

i got un lazy and goodgled, not bad for thirty bucks!

http://netwelding.com/prod02.htm