This is the stock seam on the rear of an F-1 truck cab. Read the reply to learn some diffe
Q. Ron, thank you for the service your column provides us "wannabe" craftsmen. I want to weld the body seams on my '51 Ford F-1 and keep the body lines. I have oxyacetylene and flux-core MIG welders available, but no TIG, which I understand from your previous articles you would prefer. Is flux-core MIG welding or oxyacetylene better for my purpose? I did weld up some holes in the firewall with the flux-core wire. Wow-those welds were so hard to grind! Is there a softer flux-core wire I can purchase?
One last thing: How do I get the paint out of the seam in preparation for welding? I have owned this truck for 40 years but have not driven it in the last 35. I sure want it to be right this time!
Via the Internet
A. There are a few options for filling your roof seam, but the first step is to define your goal. Apparently, the original seam above the rear window is tight, and I don't see any signs of rust damage. If you carefully prep and paint that area, it should last as is for at least another 55 years!
The only advantage I can see to welding the seam is to create a tiny fillet at the base so it better matches the look of the roof in the area behind the door glass. If this is the goal, an easy way to make a pretty darned nice fillet is to use seam sealer. This is used a lot in modern car construction to fill seams of many different configurations. You can buy seam sealer from automotive paint stores, and it's really easy to apply! You'd have to look VERY closely at an inside corner seam properly treated with seam sealer to detect that the seam wasn't welded. The reason I'd suggest seam sealer for this job is because it's designed to be slightly flexible, so it is unlikely to crack over time. Regular plastic body filler (Bondo) isn't designed to flex, and I wouldn't trust it to fill a seam of that nature without welding it first.
If you want to weld the seam, I really don't suggest MIG welding. First of all, an MIG weld bead is pretty big, and as you've reported, it is very tedious to grind down a giant-sized weld bead. In addition, you would be grinding in a pretty sensitive area, since the "eyebrow" above the seam you welded would be in grave jeopardy of being accidentally hit with your grinding disk, and I'm pretty sure that at best you'd wind up with a lot of thin spots there, if not holes! In addition, flux-core MIG wire really isn't ideal for welding thin automotive sheetmetal. Yes, the weld will stick, but the quality of the weld just isn't up to the standards usually used for bodywork.
I really wouldn't recommend using an oxyacetylene torch for welding the seam, either. Although you could probably make a smaller weld bead than you could with an MIG welder, you'd still be faced with a lot of difficult clean-up grinding, plus the heat of the gas welding process would most likely cause significant warping, which takes a lot of extra time to repair.
I know you don't have a TIG welder, but this is one of those situations where it is really the ideal process. With a TIG machine you could lay down a really tiny weld bead right in the base of the seam, and it probably would require VERY little grinding, and I wouldn't expect it to cause much distortion in the roof panels, either. It is important to use very tiny filler rod for a sensitive job like this-I'd use .035-inch-diameter rod-DEFINITELY not 1/16-inch! Once the seam was completely welded, you could even out the fillet with plastic body filler with no problem. (Your fingertip can work great as a squeegee here!) Perhaps you can borrow (or rent) a TIG welder. If that's not feasible, it really might be worthwhile to hire an experienced TIG welder to do this portion of the job for you.
Getting back to the difficulty of sanding an MIG weld bead-just for the record, there is a solid MIG wire (not flux-core) called Spoolarc Easy Grind, sold by ESAB. It's designed to sand more easily than regular solid MIG wire, but it's just as difficult to hammer (MIG welds, as you've learned, are HARD).
For the small, horizontal portion of the seam where both sides fit flush, this can be easily MIG welded, then sanded flat, and any tune-up work can be done with plastic filler. No eyebrow, no problem! Of course, if a TIG machine is available, sanding the weld bead will be greatly eased, since it will be much lower profile.
You have a few options for cleaning the seam. I normally use a 3M Clean & Strip disk for tasks like this-it's pretty fast, and it will get fairly deep into a seam. A rotary wire brush will get just a little deeper into the groove than the 3M disk, and in fact, it could be used to do the entire job, although it's slower. Sandblasting will get more deeply into the groove than anything, but be very careful about sandblasting large areas of sheetmetal away from the seam, since it is really easy to warp panels unless you have learned the proper technique.
Now you can e-mail your questions to Professor Hammer: E-mail firstname.lastname@example.org or mail to: Professor Hammer c/o CLASSIC TRUCKS Magazine, 774 S. Placentia Ave., Placentia, CA 92870. We'll print your name and city unless you request otherwise. Ron Covell has made several metalworking videos and offers an ongoing series of workshops across the nation covering all aspects of metalworking. Check them out online at www.covell.biz, or call for a current schedule of workshops, or for their free catalog of videos, books and fine-quality metalworking tools. Phone 800-747-4631, or 831-768-0705. You can send a request by mail to: Covell Creative Metalworking, 106 Airport Boulevard #105, Freedom, CA 95019.