Ron is demonstrating a very simple, but effective way to make many bends in bar stock with excellent repeatability. A "former" is cut to size, clamped to a workbench, then the bar stock is pulled tightly against the former, wrapping it from one end to the other. This technique is ideal for any project that requires making a number of pieces with exactly the same curvature.
You can email your questions to Professor Hammer at covell@cruzio.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 Boulevard #105, Freedom, CA 95019.
Q. Do you have any suggestions for bending 1/2-inch-diameter cold-rolled steel bar to the same contour repeatedly? I'm trying to make the sides of my buck, but I need a way to make the slightly curved pieces accurately over and over. Thanks for any help.
J.P. Machado
Via the Internet
A. This can be easily done by cutting a "former" from 3/4-inch Plywood or MDF. The former is cut with a band saw (or saber saw), and then sanded to have a radius curved a little more than what you want the finished steel bar to have, since the bar will spring back a certain amount after bending. You'll have to experiment to find the curvature your former requires to give you the result you want. While you'll probably have to adjust the curvature of your former a few times, once you have it "dialed in", you will get excellent repeatability by using this simple technique.
I usually clamp the former to a workbench horizontally, and place another block of wood (a stop) near one end, with just enough room between the stop and former to place the bar into. To make the bend, you place one end of the bar between the stop and the former, and pull the bar around so it makes contact with the former along its entire length. It's hard to get leverage on the last little bit of the bar, so it may be helpful to cut the stock long enough to make two pieces, and bend one end in the fixture at a time. This will give you a nice "handle" to pull on for making the bends, and you can cut the piece in half after bending both ends.
Working on a flat surface, like a workbench, will allow you to keep the bar in contact with the bench all the way through the bend. This will ensure that the bend remains flat, rather than taking on a twisted corkscrew shape, which is hard to correct if it occurs.
A common mistake people make when using a former is trying to press the bar against it by holding both ends of the bar in their hands, and pushing the bar against the former with the first point of contact in the center. When bending this way, you will often develop an air gap between the bar and the former in the center, since the center of the bar can bend more easily than the ends. The trick is to capture the bar against the former at one end, and wrap it continuously against the former from one end to the other. This eliminates any air gap, and your bends will be impressively uniform!
Q. I just wanted to let you know that your video TIG Welding Basics is fantastic! My new TIG welder arrived Friday, I watched your video Saturday, and after a bit of practice I was applying my new craft to one of my vintage projects that evening. The superior control the TIG gives me over MIG welding is wonderful.
My question: Back in the '60s, Lotus welded the tube frames of their racing cars with oxyacetylene torches and nickel bronze filler rod. From what I understand, it provided a strong weld with a bit more flexibility that safeguarded against failure from fatigue. I picked up some silicon bronze filler rod to try on the sheetmetal, and I like it very much. It's good for keeping the temperature low, and the bronze seems to flow along the seam to really penetrate the junction between the metals. Is silicon bronze filler rod as good as the old nickel bronze? Are there nickel bronze rods I should consider, and do you think I should even consider this type of TIG welds for structural repairs on tubes etc?
Bill Bartlett
Via the Internet
A. I'm delighted that you enjoyed the TIG DVD, and that you purchased a new TIG welder! TIG welders are definitely more expensive than MIG machines, but with an excellent new machine on the market from a major manufacturer with a street price around $1,300, quite a few home hobbyists are stepping up to TIG welding, and discovering its many advantages!
Silicon bronze has about half the tensile strength of mild steel, and one quarter the tensile strength of chrome-moly steel, so I wouldn't recommend it for all repairs or fabrication. It certainly has its place, however, since not all joints need to have the same strength as the base metal, and the bronze rod flows beautifully, so it can fill some pretty good-sized gaps, if necessary. It also causes much less distortion than steel filler rod, which makes it well-suited for a number of applications!
I got to tour the Lotus works in the mid-'60s, and saw lots of bronze-welded chassis there. I'm not certain what rod they used--some have told me it was silicon bronze, but I'm really not sure. There are many alloys of bronze available--phosphor bronze and nickel bronze are two examples, but I'd stay with silicon bronze for the type of work that you are doing. For the record, the English racing car fabricators switched to steel filler rod and TIG welding decades ago.