Mark Aspery Posted February 18, 2009 Share Posted February 18, 2009 I wanted to look at some of the ways metal moves on its own accord as we work. The first example is a collar. So often a collar is a bar tack welded to the bits that need collaring and then pulled around the group with the use of a torch. I wanted to show the distortion of the metal as it goes around a bend without any correction by the smith. Photos 1 - 3 A bar was bent in a tight radius and then cut in half to examine the results of the bend. The last photo shows a collar where and the lipping and cupping has been addressed through forging over a mandrel. Photo 4 This same problem exists when we make hinges. If you remember Gerald Boggs's "Butterfly hinges" thread and photos, he mention a pre-cupping of the bar in the opposite direction to offset the cupping effect caused by bending. Quote Link to comment Share on other sites More sharing options...
Don A Posted February 18, 2009 Share Posted February 18, 2009 Thanks again, Mark, for making us think. I have a pending job for 22 pintle hinges, and I remember clearly battling the distortion on the last set... mainly just trying to beat the barrel edges true around a piece of round stock after they were rolled. Thanks to all of the good instruction, I look for this next set to go much smoother. I appreciate it, Don Quote Link to comment Share on other sites More sharing options...
Mark Aspery Posted February 18, 2009 Author Share Posted February 18, 2009 Thanks again, Mark, for making us think. I have a pending job for 22 pintle hinges, and I remember clearly battling the distortion on the last set... mainly just trying to beat the barrel edges true around a piece of round stock after they were rolled. Thanks to all of the good instruction, I look for this next set to go much smoother. I appreciate it, Don I would take a bar the same size as the bar you intend to use in your hinges and bend it to the same radius. Look at the cupping that takes place and try to match it with a fuller or bar-stock. That is how much you have to bend the material the other way to offset the lipping/cupping effect taking place during bending. It's usually not much, a cheese fuller in a 3.5 inch bottom swage (or piece of pipe) is a good place to start. Quote Link to comment Share on other sites More sharing options...
CurlyGeorge Posted February 19, 2009 Share Posted February 19, 2009 Thanks Mark. I didn't realize that pre cupping in the opposite direction would take care of that. But it DOES make good sense. Thanks, again. Quote Link to comment Share on other sites More sharing options...
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