A circle cutter is one of the original rotary hand-crank machines patented first in the early 1800s for tin and copper smith trades. It is designed to easily cut perfect circles out of sheet metal of a traditional gauge (thickness) and not only made exact edges (which makes life a lot easier on the burring machine later) but saved a ton of time so a person didn’t have to hand-cut each circle. Circles are used a ton in traditional coppersmithing, and are still used today to create custom orders or reproduction wares. We use circles for bases, covers, and lids, among other things, and most builds use a circle in some way. This is a wonderful time saver.
The first thing to do is to discover if your circle cutter cuts on the radius or the diameter. The radius will require additional math every time you want to cut a circle.
When cutting a circle, first you must discover the final diameter of your final circle size, plus include the burr for your seam allowance if you are putting in a rim band on a lid or burring up the sides to finish a base of a pot or cup. These numbers will vary for every single design.
For example, you have a 8” circle you want at the end. However, you are going to be burring it 1/8 of an inch to go up the base of your pot. Because you have to account for the 1/8 on “both sides” of the circle, as it were, you will want to cut a circle that is 8 3/8” to build in a little wiggle.
With the final circle size, you will cut a blank square that will allow for some waste as you run the material through the circle cutter. For our example of a 8 3/8” circle, you will want to cut, to give yourself some breathing space, at least 8 5/8” x 8 5/8” square. Or to make it easier on yourself, just cut a 8 ¾” x 8 ¾” square. Mark the middle of the square with a dry erase marker, which in this example of a 8 ¾” square would be at 4 3/8”.
Set your cutting measurement on the machine to a 8 3/8” circle. (If you have a machine that cuts on the radius, you will have to account for dividing your measurement and setting the circle cut accordingly.)
Place the square in the circle cutter and run about 1/16” of the material through the cutting face until you hit the center dry erase mark in the center of the cutting wheel. Clamp down the material on the left. To be precise, you can always measure both sides of the material exposed on either side of the clamp to be sure the exact amount is showing.
Run the material through by turning the rotary hand crank and voila! You have a perfect circle.
I love this machine. It makes coppersmithing life sooo beautiful!