To begin with the fabrication of your coin ring, you will need to remove a small amount of material from the center of your chosen coin. The size of the hole will usually be just large enough so that it will fit over the small end of your tapered steel mandrel. Most common ring mandrels will require that the hole be around 7/16" to 1/2". If the final ring size you are trying for will be a size 9 or larger, then generally you could make the hole in the coin a bit larger than 1/2". As you gain more experience, you will learn better how much material needs to be removed to achieve a certain ring size.
Some will anneal (soften) the coin before attempting to drill or punch the hole. Again, it depends a little on the type of material the coin is made out of whether you will need to anneal it first. In most instances, you will not need to anneal the coin first. The hole in the coin can be done in essentially two different ways. You can either punch the hole with a punch and die set, or you can drill the hole using a powered hand drill or a small bench mounted drill press. After drilling or punching the hole, usually the cut edges will require a little deburring. This can be done with a small rat-tail file.
The placement of the hole should ideally be as near as possible to the exact dead center of the coin. There are several methods for locating the center of your coin, and here is one. However, DO NOT obsess over the placement of the hole, if it does not end up exactly in the center. There are at least two ways to fix a hole that is slightly off center.
Here are the two ways to fix the hole in the coin if it is slightly off center.
- The first involves using a small rat-tail file to remove metal around the hole on the side where it is the thickest. You can usually do this by eye, or you can use a calipers to measure the distance from the outside edge of the coin to the inside edge of the hole.
- The second way is to wait until you start forming the coin down the mandrel. As the coin is being formed you will notice that one side of the ring is thicker than the opposite side. Using a flat file you can remove material from the edge of the hole where it is the thickest, until the width of the sides are more even.