Welding 1/4" to 1/8" Help

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I am welding a small frame together using my Lincoln Pro Mig 175 with FCAW on 1" X 1" X 1/8" wall.  Part of the frame requires a couple pieces of striaght 1/4" thick plate to be welded to the 1/8".What is the general rule to get good penetration on the 1/4" but not burn through the 1/8"?I did a few test welds leaving the weld speed and temp for the 1/8" the same and welded the 1/4" to it.  The welds looked and sounded good.  It looks like I pentrated close to half of the 1'4" material on each side.  So I would assume I have a solid weld.From what you would think you can only use as much heat and speed for the thinest metal you are welding.Thanks in advance!
Reply:I think if you do a search on this site this has been discussed before, but I may be wrong. It might have been on a different forum, but think it has been discussed here in the past, never hurts to bring it up again anyways.I think you need to set your welder up for the thicker material and mainly weld to it and butter over onto the 1/8 inch material.  Doing so you should have adequate penetration on your 1/4 inch material.
Reply:Did you bevel the 1/4" plate?  With proper joint prep, you should have no problems.  Hank
Reply:I agree you need to have enough heat to weld the 1/4 , then concentrate most of the heat on the 1/4 and weave it over on the 1/8 to complete the weld.Welder- Miller Thunderbolt AC 225-DC 150 Plasma cutter, Miller Spectrum 300O/P torch- Victor 100
Reply:Ok, so basicaly keep most of the heat on the 1/4 and then use an up and down motion hitting ther 1/8 for a second?  Is there some kind of timing I should use to be sure I cam putting enough time into the 1/4 and 1/8?  Someone once said when weaving up and down you count 1...2.. and then move and start over.How much movment should I do like and 1/8 ince up and down?Thanks!Build a Barstool Racer at BarFlyRacers.com!