The key ideas of the design is that has a wide edge to get a much broader grip under the paint can's lid (spreading pressure across a broader area), an upturned lip at the tip to help grip the lid, and an arc ground into the broad side of the edge that allows the tool to connect smoothly with the round lid.
The tool is very solid (probably more solid than it needs to be -- I'd recommend using thinner steel stock), feels good in the hand, and is easily kept in a pocket while working.
The next few steps describe how I went about making it.
Step 1: Step 1: Cut Out the Basic Shape From a Steel Blank
I scribed the shape of the finished tool that I wanted out of the existing steel and cut the shape out with a vertical band saw. The second picture shows the cut plan from the original stock. The third picture shows the tool blank.
Step 2: Step 2: Drill the Hole for Hanging Tool When Not in Use
Step 3: Step 4: Shape Ends With a Grinder
To get there, I used a disk sander and series of grinders to make the desired shapes at both ends of the opener. Small end for small cans (no arc, just a lip), big end for bigger cans (arc + lip).
Step 4: Step 5: Polish and Use
The first cool project that lets me say "I made it at Techshop" -- www.techshop.ws. More to come.