Penetration is controled by amperage and flow is through voltage. Flux core is basically stick welding as there is no need for gas, the flux is the shield against O2 contaminating the metal in the moltant state.

 

One way to find a good setting with a mig is to start the wire running on a scrap piece and adjust the wire speed up or down until is sounds like bacon frying.

 

That is true, but also not so much. That figure will give you single pass at full penetration. Short circuit MIG only needs 21-22 volts ( 75/25 Ar Co2 gas) and 180-190 amps for a way more than sufficient weld for most applications. Full pen welds are not always needed...it just depends on the application. I can weld 1/4 very easily with my Miller 210 MIG and have it stand up to anything you could throw at it. Most would be very surprised at how little penetration is needed for a weld to do what is needed. I know I was when I began destructive testing welds.

Bottom line, with proper technique and setup, the 175/180 class MIG's can weld 1/4 adequately for most applications.

 

mmmm...bacon.

 

How much to rent? I never thought of that. Does the kit they sell work out of the box? Or do I need to buy wire and whatever else a mig welder needs?

Of course I need to buy the safety gear as well.

 

The Home Depot rental was something like $33 (4 hours) or $44/day. It came with gloves and mask. I had to buy a spool of wire. I think that was $9.

Some guy came in right behind me to rent the welder. Home Depot only had the one. I got his name/number and when I was done, I went and did his job. He gave me $30 cash.

 

Bacon sizzling, yep, that's what I was gonna say. You know how they taught us how to weld at the welding school I went to. Well, at least with the teacher I had for over a year and a half. He had been welding for 25 or 30 years and knew his stuff.....anyhow, I read the book, for Mig, then answered the questions at the end. He then stuck me in a booth, said, "Go dig around outside and find some scrap metal and play with it for awhile". So I did that for the rest of the night. Next day he said, "Go get some scrap from outside, bevel the edge at a 45 degree angle, don't make it to thin, butt the two pieces together and make your first pass, then a cover pass". He told me you wanted a thin line on the other side, showing that it penetrated. After many days of doing this flat I got confident. So I cut my plate into 3, two inch wide sections and he put them into the press to stress test them. They all cracked, some in the center, some at the edges. Back to the drawing board. I'd say I worked on that for about 5 weeks, night school, three times a week for about 4 hours a night until I finally got enough practice to run a solid bead, a cover pass that would hold up under the test.

That was just the beginning. Next was welding horizontal, vertical up and then vertical down and lastly, overhead. Each time I started a new position I thought, no problem, I just did the flat and passed, or I did the horizontal and passsed. It was not that easy, seemed like there was just a little bit of a difference in the technique to get a good strong weld. Maybe that's just me, but by the time I was done with the overhead welding part and saw my pieces get bent all out of shape and no cracks.....I was darn proud of what I did.

Basically, long story........long, practice, practice......and more practice. Stop by your local welding shop and ask if you could pick through there scrap metal bin.....tell them your going through welding school and the program is under funded and you need some scrap to practice on. I was actually in school, but it worked out great. I got a bunch of steel from several places and they were all willing to let me dig around there metal bin. It helped out for the other people at school the night I came in with a truck load of practice metal!!!

 

The posistion has a lot to do with the voltage, verticale being the most delicate in the heat. Adjust your machine to 16 volts on verticale and adjust your wire speed to that and then step it in on the first pass. And yes experience, you can't buy just got to put in the time.