Getting tack welds on thin aluminum sheet can be tricky. In the letter below, Ron shares s
Q: I've attended a couple of your aluminum workshops at Fatman Fabrications in Charlotte, North Carolina. I not only learned a great deal from the workshops, but I found them to be very enjoyable as well.
Even though I observed you tack weld thin aluminum sheet with the TIG welder several times, I continue to have a problem duplicating the process consistently. Too often, I either contaminate my tungsten or melt away a spot before I get the two sheets joined. I'm talking about a butt joint with good line to line contact on aluminum sheet .030- to .060-inch thick. I'd appreciate any thoughts or advice.Jerry HenryVia the Internet
A: First of all, if your problem is contaminating the electrode, that is fairly easy to remedy. Simply put, if the electrode gets contaminated, you are probably touching it to the base metal, or perhaps to the filler rod. If you don't touch these with the electrode, that should eliminate the contamination problem. One other conceivable cause of contamination is if you don't have a proper argon gas shield because of insufficient gas flow or if the electrode is sticking out too far-either one of these could cause contamination, too. I use about 1/8 inch of tungsten stick-out, and about 16 to 18 cubic feet per hour of argon flow.
Basically, .030 aluminum is much more difficult to make a butt-weld on than .060, but both are possible. I'd recommend practicing on the thicker material to build up some proficiency with your technique, then when you're comfortable with that, move on to the thinner stuff.
One thing that really helps for tack welding is to rest the torch's torch cup on the metal, then pivot the torch until the tungsten is the proper distance from the base metal (usually about 1/8 inch), and point it right at the center of the joint before you hit the foot pedal. Then when you start the arc, you can continue to pivot the torch on the cup's contact point until you get the arc properly aimed, so both sides of the joint are getting equal heat. Once the arc is centered, start building up the heat until you just barely have a puddle, dip a bit of filler rod into the puddle, withdraw it, and then extinguish the arc. You should never touch the cup to the base metal when welding a seam (it will cause the torch to move in a jumpy manner), but for tack welding, it's a real advantage to rest the cup on the metal and use that point of contact as a pivot for the torch. You may have to practice making a tack weld hundreds of times to get really proficient with it, as most welders have (yours truly included).
I don't know if you are aware that I have recently released a new DVD on TIG welding. The DVD shows proper machine and joint setup, and how the process works when everything is done correctly, but it also shows most of the things that can go wrong.Contact me again if you want more details on any of this.
Q: I'm writing again with a question regarding my '40 Ford pickup restoration. I have been trying to remove the doors from the truck, but I can't get the hinge pins out. I tried spraying them with WD-40 two or three times a day for most of a month, but it didn't help. I've tried using heat, but again, it didn't help. Drilling the pins out could make the hinges useless if the drill wanders even a little. I don't know what else to try-any suggestions?Dean DavidsonVia the Internet
A: WD-40 doesn't always work, but using heat has never failed me. The correct procedure is to heat the hinge bodies as quickly as possible with an oxyacetylene torch until they are a dull red color, then quickly tap the hinge pin up with a punch just slightly smaller than the hinge pin. It may help to have a buddy hold a heavy weight against the hinge body as you hammer on the pin to counteract the force of the hammering.
You can e-mail your questions to Professor Hammer at 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 their free catalog of videos, books, and fine-quality metalworking tools. Phone 831-747-4631 or 800-768-0705. You can send a request by mail to: Covell Creative Metalworking, 106 Airport Blvd., #105, Freedom, CA 95019.