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Q. I need your advice about fixing dents in polished stainless steel. I've decided to restore the original grille for my '49 Suburban instead of purchasing a reproduction. As you can see in the attached picture (at right), the dent extends into the crease. What tools should I use, and which side do I hammer on? Do you work with stainless any differently than regular steel?
Via the Internet
A. Stainless steel is an interesting metal. You might think of it as "mild" steel that has had a strong percentage of nickel and some chromium added to it. These elements prevent the material from rusting or corroding, so it can be polished to a high luster and the shine often lasts for decades. The nickel content "toughens" the material, but fortunately, the alloy used for trim on trucks is relatively soft. (Many people are surprised that stainless can be both tough and soft. This means that stainless is difficult to cut, but it can be dented or straightened with a hammer and dolly fairly easily.) Stainless also work-hardens faster than mild steel, so you want to carefully plan your strategy for straightening the parts, and try your hardest not to overdo any step, since you can't go "back and forth" with stainless nearly as much as with mild steel. While some stainless trim is extremely thin, I think your truck grille bars are about 20-gauge, and this is thick enough to give you a "safety margin" for metal finishing.
While you could start with a hammer and dolly, I'm going to recommend another technique. Cut a piece of hardwood roughly 1-inch square and 10 or 12 inches long, and carefully sand one end to be a close match to the contour of the inside of the grille bar in an undamaged area. Next, put a smooth hardwood block on a workbench, and place the grille bar upside down on top of it, so the part you want to straighten is supported by the block. Now, using the piece with the shaped end, locate the nose right at the edge of one of the dents, and tap it lightly with a hammer. You should tap with just enough force so that you see the metal move a little with each hammer blow. The strategy is to start at the edges of the dent and work toward the center. In the beginning, you will have an air gap between the dent and the block it's resting on, and as you tap the metal down, the air gap gets smaller and smaller. As soon as the dented area touches the wooden block, move closer to the center of the dent. If you hammer too much, you risk stretching the metal, which will make an "out" dent that will be hard to repair. You should be able to get 80 or 90 percent of the damage out this way. Don't do any hammering on the crease area-it's possible that with the small amount of damage you have, straightening the rest of the grille bar may cause the damage in the crease area to come out automatically.
When you have done as much as you can with the wood blocks, any remaining uneven areas can be worked with a hammer and dolly. As with any metalwork, you hammer off-dolly to bring any high spots down, and on-dolly to bring any low spots up. Be extremely careful not to hammer on-dolly any more than necessary, since if you go too far, it's very difficult to get the metal back down.
If the crease area still needs some work, I would find or make a piece of steel that is a good fit into the crease from the front. This should be 3 to 4 inches wide, made from plate 1/8- to 3/16-inch thickness to offer the part adequate support. (Hint: A brick-cutting chisel may be good for this!) Hold this tool in a vise with the "business end" pointing straight up. Now you can carefully position your grille bar over this tool, so the tip of the tool is nestled exactly in the center of the groove, and carefully tap any high (when seen from the back) areas down with a hammer, until the air gap is gone.
The finishing step is to carefully file or sand the face of the bar to reveal any minute low spots, and work these up with careful hammering. When all the low spots are removed, the part will be ready for repolishing!