reverse polarity

[JDeereGn]

I wire weld with a Millermatic 251. I know I am supposed to reverse polarity when welding with flux core wire. WHY?? When I have been in a hurry to do a small project outside and not reversed polarity I can't tell the difference. Am I that bad a welder?? Thanks for any info

[aametalmaster]

Did you happen to be using flux core that uses gas? it runs on the same welder settings as solid steel wire. Just a thought...Bob

[JDeereGn]

Bob, I didn't know some flux core wire required gas. I will check the box.

[beamwalker]

if you dont reverse it with flux core it will give poor weld. lots of pinholes and b b s will come off puddle. tried it a few times. dual shield uses gas and is flux cored

[Tacker Beau]

I have pretty much read this whole web site over a hundred times in the pass few weeks, hunting down the right hobby shop mig. I finally decided, MM 210, was for me ( also going out of stock, the price was great!). Then I started the learnig process, pouring over the manuals and such, and came up with a query maybe you folks could help me with. When I left the dist., I grabbed a box of the gasless flux core wire, as I won't be home until after the new year, and want to play a bit with the new toy. The polarity change, seems a bit spooky, but I don't have aproblem with it if I'm doing the right thing. The box tells me nothing, but after further search, the spool it's self does say Gasless Flux Core. The alloy #E71T-GS .035.
Stupid question maybe, I'm just a little on the jumpy side when it comes to changing stuff on a new thing like this and thought I should ask first!
Thanks for the reads, Beau

[aametalmaster]

Gasless flux core wire uses the ground that is positive + and the gun is negative- backwards of regular solid wire welding....Bob

[AnotherDano]

Stupid question maybe, I'm just a little on the jumpy side when it comes to changing stuff on a new thing like this and thought I should ask first!
Thanks for the reads, Beau

There should be a very clear diagram glued to the inside of the hinged cover on your machine. They make the polarity change as easy as possible. Usually just a matter of two wingnuts, swap the wires and tighten them down again. Just follow that and you'll be fine.

[Tacker Beau]

Thanks for the replies! Fingers crossed and ready to fly! Beau

[beamwalker]

I have pretty much read this whole web site over a hundred times in the pass few weeks, hunting down the right hobby shop mig. I finally decided, MM 210, was for me ( also going out of stock, the price was great!). Then I started the learnig process, pouring over the manuals and such, and came up with a query maybe you folks could help me with. When I left the dist., I grabbed a box of the gasless flux core wire, as I won't be home until after the new year, and want to play a bit with the new toy. The polarity change, seems a bit spooky, but I don't have aproblem with it if I'm doing the right thing. The box tells me nothing, but after further search, the spool it's self does say Gasless Flux Core. The alloy #E71T-GS .035.
Stupid question maybe, I'm just a little on the jumpy side when it comes to changing stuff on a new thing like this and thought I should ask first!
Thanks for the reads, Beau

that wire will be just the opposite of stick. your gun should be hooked up to - and ground to +

[fun4now]

changing the polarity is a simple thing, they made it simple so people would be able to change over quick and easy. you will not hurt the welder. its about putting the heat where its needed. i suspect they want to melt the flux core differently to get the flux out and working fast as apposed to being pulled into the weld where it would cause flaws like pin holes. yes it will stick the 2 pieces together even in the wrong polarity but the weld wont be nearly as strong. same goes with re-setting it when you go back to solid wire with gas. the welds will be much colder if you don't switch back.

Tacker Beau
congrats on the MM210, i really wanted to get one before they were all gone. looks like i missed my shot. the MM212 is nice but i really like the look of the 210 better.

JDeereGn
as for being a bad welder, i suspect you would just have to take a closer look. possibly cut the weld open and take a look-see.