Above is the finished press die installed on a 1/4 inch thick aluminum disk (bolted on utilizing the hole I drilled and tapped on the bottom of the steel owl skull form). The copper piece in the center is the first failed attempt at pressing copper sheet. You can see the copper decided to fold along the edges, so I had to figure out something to do about that. The copper piece on the right side is the next attempt, which was successful after I figured out what to do about the folding problem.
And a view from the bottom.
I also changed from cutting out a 2 inch diameter circle of copper sheet to using larger rectangles. Easier cutting, and with less critical issues getting the press die centered in the middle of the metal, fewer gaps. Note the red center line I’ve drawn on the fully annealed rectangular sheet to help centering the die in the press. By the way, there’s nothing special about this sheet of copper – it’s just an inexpensive 18 gauge sheet from the hobby metal display at my local Ace hardware store.
Above, I’ve placed the urethane container, sheet metal and press die in my little hydraulic press. I’ve slowlyy raised the ram until all the parts are in contact with each other, then carefully centered everything. I’ve also made certain the parts are directly above the hydraulic ram. I don’t want anything to get caddywhompus, because that might cause something to be ejected at high velocity – I value all of my parts and would prefer not to be injured! By the way, proper safety equipment like eye protection is a must here! Here’s a link to a build-along of a press similar to mine.
Above, I’ve begun squishing the die down into the urethane. You can see the copper is beginning to take the shape of the die, and starting to fold along the edge. It is this folding we need to watch carefully, and take action to correct before going too far.
Above, I’ve removed the die from the press. The folds on the left side (bottom of the image) are almost too far gone. I had to do a little fancy planishing to hammer them out. Don’t let them get this bad!
Above is how to fix the fold problem. I’m using the horn of my anvil as a planishing stake and gently hammering on the “up” side of the fold (the top of the hill). In this case, you can see there are two “up” folds here.
Above, I’ve completed planishing (hammering) the two “up” folds flat, and need to do the other side. Hopefully, you can see the cup I’m beginning to form on the planished/hammered side. I want this area to be in a cupped shape, and not back to plain flat sheet. This will help with the pressing, reducing fold formation a bit. However, you don’t want this to be so deep of a cup that the copper sheet will hit the press top before the aluminum base of the die does.
Above, I’ve planished all the folds away. Notice this time I’ve begun planishing the end of the beak as well. Notice the cup forming, and how the edges of the copper sheet are no longer straight. The edges are being pulled in towards the areas where the most deformation is occurring. This is a good sign, because it means the copper isn’t being stretched and thinned too much by the pressing.
Above, the fourth and final pressing. My copper sheet rectangle was a little narrow, or I didn’t get it quite centered. This side is a little short, but still usable. By the way, I made my steel owl skull form a bit taller (top to bottom) than the finished piece will be, just to accommodate problems like this.
Above are the failed original and the three successful pressings. You can see the high degree of repeatability in the process. The skull in the upper right is the one we’ve been working on in this posting.