[Gabbyp]

I have a Lincoln SP250 which I bought 20 years ago. This is a 250 amp 220volt machine which has their microprocessor controller for machine settings. It asks for wire size and type, material thickness, type gas, and then uses Lincolns settings for those conditions. It has the ability to adjust IPM and voltage settings if needed. Most of the time it has been spot on for all my projects. However I am trying to weld in interior patch panels on my 52 AD. When I clean up the original rusty steel the thickness is reduced, and when I use the new 20ga panels, I cannot prevent burn thru on the old using the new 20 ga machine settings. If I adjust to a thinner gage I don't get good penetration on the new 20 ga panels. My question is what should I adjust, wire speed or voltage. The machine has a stitching function, weld on, weld off. I could experiment but there should be some helpful hints from fellow members, especially Oldred, who I'm sure have experienced the same conditions. I am using .023 ER70S-6, C25 gas. I have also tried JW Harris Twenty Gauge wire for thin steel but no success. I contacted Harris and got a reply from Lincoln, Lincoln owns Harris. They said that wire was designed for 110 volt machines. Doesn't make sense to me. So any thoughts would be appreciated. Thanks

[speedydeedy]

The only thing I could suggest is set for the thinner metal and pre heat the thicker metal,or after 20 years maybe it is time to buy a new Lincoln mig.I have one for 3 years now and it works great.No processor,I set it where I want it and no problems. Good luck.

[oldred]

Welding something as thin as what you have there can be extremely difficult and is going to take a lot of patience. The Twenty gauge would be my first choice with C25 gas (for either the Twenty Gauge or solid wire) next choice would be .023 solid. You need to skip weld and don't try to run beads here just a series of tacks until the seam is complete and if you can try to get a heat sink of some type behind the metal as a back up, a piece of Copper pipe flattened on one end and placed against the back of the weld can do wonders. Your machine should do just fine as long as you can "fine tune" the settings and with the Twenty Gauge wire you should be able to weld as thin as 24 GA but it will take some practice to nail down the technique. I am puzzled as to why they told you the Twenty Gauge was better on a 110 welder , a 110 machine will certainly benefit from the Twenty Gauge but that wire will run just fine on a 220 welder and in fact it would not know the difference, maybe on a big industrial machine that might not turn down low enough but your machine is just fine. Make sure you have the polarity set right, reverse for the Twenty Gauge, and use the C25 gas along with the backup if possible and you should be able to make this work.

[F&J]

You need to skip weld and don't try to run beads here just a series of tacks until the seam is complete

That's what I've done for years. I thought I was the only one

Some friends look at me welding fairly flat, thin, areas like doors, and they wonder why I am "diddling around"...

I've seen so many posts on the web about destroyed panels from long beads.

I use a big old Miller 35s with 35 wire and I rarely burn through using it

[kringold]

Originally Posted by Gabbyp

I could experiment but there should be some helpful hints from fellow members, especially Oldred, who I'm sure have experienced the same conditions.

Do what Oldred said and you should get it. As usual, he's right again.

[NEW INTERIORS]

I would keep the heat up,But try to stay on the 20g a little more then the light panel.Work off the bigger panel.One spot at a time.Use the .023 wire you don't have to run as hot as the bigger wire.

[Gabbyp]

Thanks for all the inputs. I will be trying them and report back on what worked.

[Gabbyp]

Success! I followed Oldreds suggestions and it works. I used a copper backup and stitched the welds. I went again to JW Harris web site and read the tech sheet for Twenty Gauge and found their parameters were significantly different than the SP250 program. SP250 was 14.8 volts and 80 IPM versus 15 volts and 150 IPM. I used these setting with a stitch time of 0.6 sec and it worked great. I then saved this setting in the SP250 memory. I guess the old adage applies to me, read the instructions first. Hope the attatchment work to show a test strip I made. Again I want to thank Oldred and new Interiors for their help