Q. I read your articles every month in CLASSIC TRUCKS, and enjoy them! I hope you can help me with my plan of attack for fixing a rear fender on my Suburban. I've attached an "on-truck" photo of the fender.
By following your techniques, I have been quite successful in restoring a '47 and '51 Chevrolet pickup, and would call myself an above-average amateur metalworker. I'm concerned about the Suburban, because when I was working one of my '51 pickup fenders, I had problems with it cracking from the bottom edge, and I had to go back and weld it up two or three times. Was there something I was doing wrong? I hope you can assist me with the correct approach to use on my Suburban fender, before I attack it.Patrick PlummerVia the Internet
A. Patrick-I'm glad you enjoy the column, and that it has been helpful for you! I'm a bit puzzled why your '51 fenders cracked repeatedly-this is certainly not normal! First of all, I presume they cracked AFTER you repaired them, probably once you started driving the truck again. If they cracked when you welded them, or shortly thereafter, there is something going wrong during the welding process.
Normally, a weld made with full penetration on metal that's full thickness will be just as durable as an uncracked and unwelded fender. Since your '51 fender cracked that many times, something is not right. I'd be suspicious that the weld may not have had full penetration. You can tell if a weld has full penetration by looking at the back side. The weld usually melts completely through the metal, leaving a clearly defined "bump" on the back side. If this melted-through section looks fairly consistent, then you have full penetration.
So, assuming the weld is good, what then could cause the repaired area to crack again? My first suspicion is that the metal has been thinned, and therefore weakened, either by excessive filing or grinding from a previous repair, or perhaps by rust or corrosion damage. The best way to repair these conditions is cutting out all the metal that is too thin, and replacing it with new, full-thickness metal. You are much better off replace a little extra metal, since if you're too stingy, and leave any metal of questionable thickness, you'll be asking for trouble later.
One other factor that can cause premature cracking is allowing the fender to vibrate. Sometimes fender braces fall out or break. This can cause vibration and the eventual cracking of the fender. Sometimes other factors, like driving at high speeds over very bumpy roads, or driving with massively out-of-balance wheels can cause cracking, too.
I hope this answers your questions-but feel free to write again if questions remain. The damage to the front edge of the fender doesn't look too difficult to repair, and we want to see that Suburban back on the road!
Q. I want to chop the top on my '52 Chevy pickup, and I have a few questions. I've done quite a bit of metalwork, so I think I have a handle on that part of the project, but the glass scares me! I've been told that the windshield and side glass are tempered, and that tempered glass can't be cut. The glass on this truck is all flat.Syd CharlesVia the Internet
A. The rear window on most passenger cars, and some trucks, is made of tempered glass, which is virtually impossible to cut, but the side windows and windshield of your truck are made of laminated safety glass, which can be cut. Laminated safety glass has two glass panes that are bonded together by a thin, clear plastic layer between them, which keeps the glass from shattering when it breaks. This glass can be cut by scoring both sides with a glass cutting tool, then tapping on the glass until it cracks through to the plastic inner layer. Next, a flammable liquid, like alcohol or lighter fluid is squirted into this crack, and lit. The heat from the burning fluid softens the plastic, and when softened, it can be cut with a razor knife. Last, the cut edges are sanded to remove any roughness. This is a job best left to a professional, since there is a learning curve to be mastered.
You can email your questions to Professor Hammer at email@example.com, 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 many DVDs on metalworking processes, 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 and their free catalog of DVDs 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 Blvd. #105, Freedom, CA 95019.