Consistent results on automotive panels

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Hi guys....this is my second post.  First one was to introduce myself.I'm just starting a new project.  I'm restoring (and modifying) a '55 Chevy.  I recently completed a similar project for my wife, restoring a '71 Buick.  On the Buick, I butt welded patches in the fenders and the bottom 2/3 of quarter panels on both sides (had to splice hard-top quarter panels into her car--a convertible).  This required about a billion "stitches".  My results were decent on the Buick, but it seemed every day I had a different experience.  Some days I felt like I was in control, other days, I could only seem to burn holes where I didn't want them, or I'd get ugly, shallow welds.  All my sheet metal welding is done with a Lincoln Weld Pak 3200 (120v), and I always use shielding gas.  As I started welding on the '55 this weekend, it was like a flashback to the "rough" days of my first project.  I was butt welding a couple panels to the interior of the car, and achieved very inconsistent results.  I want to get this resolved before I go any further.  Here's what was happening:- Some welds seems hard to start; as if I had a bad ground or weak current.- Some welds seemed to start easily but were soon popping- I had a couple welds that didn't penetrate at all.Again, I am using shielding gas (75/25), .025 wire.  I cleaned all visible rust or paint wherever I was welding.  I tried various settings (has A, B, C and D settings) and wire speeds.  But I simply couldn't "get in the groove".    Are there any obvious things I should be doing differently?  Or any obvious placexs to start my trouble-shooting?Thanks!!Jay
Reply:I'm no expert, but one thing I have noticed that has caused a lot of inconsistency is having my lead coiled or wrapped around a corner. I mentioned this because you said you are welding inside the car, so you may have your lead making multiple bends to get in the right position. Combined with the low wirespeed for thin metal and you can have very inconsistent wire feed making it very hard to get good welds. Make sure your lead is as strait as possible and if you do have to bend it make sure its a big radius bend.
Reply:Hey Jay,Ok.... let's see if we can get you hummin' to solve issues. I do restorations on 4-6 classics a year so you have an idea of my experience & suggestions. First, auto sheetmetal is like paper, newer panels approx. 22-24ga, & older vehicles were in the 18-20ga, so you have to establish weld parameters to get good solid welds. Replacement panels are probably in the 22-24ga thickness, although heavier may be used so a caliper would provide your panel gauge. My chart shows 18ga= .040, 20ga=.031, 22ga=.025 & 24ga=.020, so you can see how thin it is.After establishing thickness, take some residual cutoff pieces of the same material, clean the weld seams at least 1/2" on each joint, & be sure your grounding clamp is close & clamped on very clean BARE metal. Next, you must use a backing....any 1/8" material of aluminum, copper or brass/bronze will suffice. I use varying lengths of 1.5" aluminum angle that makes it easier to clamp to the panel. The backing will act as a bit of a heat sink & generally will eliminate burnthru.You are good with C25 & .025 wire as that is what I use(mine is .023). I also use a Miller 110v 130A MIG for all the resto's I do. Your heat & wf settings should be in the "B" heat position, that is if it is set up as A-D(4) position. WF dial is generally 0-10, so you would need to start on the practice pieces with the wf dial between 2-3. Be sure to cut the wire after each bead or tack to insure a positive following start. Stickout should be approx. 3/8" with a gun angle of 45* so that will keep your bead flatter with less penetration. Your gas should be 12-16cfh if indoors & 18-22 if outdoors w/some shielding & with only a very slight breeze. Start you tack w/backing & examine the weld. You should see the heat line on the opposite side & then try to break it to determine if more heat or wf is needed. This preparation will give you a positive or negative result & you have to adjust from there. It will fall into place....take your time.Once you establish settings, again, insure all the weld seams(I use 1/8" overlaps) are BARE & CLEAN. Use your backing & start your tacking & alternate location to opposite sides to minimize warping. I keep a very wet towel handy to constantly cool. After your tacking is complete, I personally run 1" beads w/backing in place, alternating location & cooling quickly. Again, be sure to cut the wire after each stop.Anyway, it is not hard if you take your time & practice on some residual cutoff pieces. It will all come into focus & you will see that it is not as bad as you first anticipate. If you can, post some pics of your practice pieces so that we can point out discrepancies. I hope this will help you get started. I love resto's & the completed projects are very satisfying. I always photo the progression of completion & always give my customers a set of pics of what it took to finally come to fruition. Keep us informed. Good luck. Don't hesitate to ask anything else.DennyComplete Welding/Machine/Fab. ShopMobile UnitFinally retired*Moderator*"A man's word is his honor...without honor there is nothing.""Words are like bullets.... Once they leave your muzzle, you cannot get them back."
Reply:Thanks guys, I appreciate the advice.  I'll shoot some pix on my next effort so you can assess what I'm doing.  From your input, I can see several things I've got to address; first, I had absolutely created a series of complex bends in my lead this weekend.  Second, I haven't been using any backing.  Third, I think I'm running too much pressure from my gas.  And finally, I think I've been really inconsistent in my gun (placement, angle, direction).  But the more I think about it, the more I worry that maybe I didn't have my clamp grounded as well as I thought.  Anyway, a lot to think about, a lot to try.  Thank you for the help.Jay