Aluminum Dome

I made it at TechShop!  www.techshop.ws 
I just took my first class at TechShop, entitled Organic Sheet Metal, Safety and Basic Use.  In it, I created this aluminum dome, or bowl from a square of about 20 ga sheet aluminum.  Here’s how...

Using a paper plate for a guide, I drew a circle on the sheet. I then used a Beverly Sheer, which cuts using a hand lever and a scissor action, to cut out the circle.  After filing the edges, I was ready to start shaping the dome.

On the workbench was a sand bag that resembled a small round throw pillow, but filled with sand.  After making an indentation in the bag with my fist, I placed the edge of the disk of aluminum on the bag and began striking it with a kind of a glancing blow using plastic hammer, about an inch from the circumference. After going all the way around, I started in the center and worked outward in a spiral.  At this point, I had an ugly dented workpiece with some curvature that was warping into a taco shell shape.  The aluminum was getting work hardened, too.

Next, I took the piece to the English Wheel, and began working it back and forth between two rollers in a radial pattern. This did three things.  It smoothed out the hammer dents, it eliminated the “taco shell” warping, and it relieved the work hardening.

I then moved on to a pneumatic planishing hammer to further hammer out the dome.  This hammered the piece between a flat die and a curved die, at several hundred blows per minute.

Another tool I used was a shrinker, which had a slot about an inch deep and 1 1/2 inches wide that you put the edge of the workpiece into.  Then as you push on the hand lever, two pairs of jaws grip the workpiece and then come together slightly to shrink the edge.

Going back and forth between these tools, I formed a dome about 9 inches in diameter with almost a 2 inch dome.

What’s it for?  Well, you could use it as a bowl, make a clock out of it, use it for a hub cap, or wear it on your head to shield you from alien mind control rays.