2 x 4 inch lumber scraps (2 x 2 inch or similar also works)
drill bit gauge
fine toothed scroll saw blades (varies with gauge of wire used, but something like 40 - 60 tpi should work - thinner kerf is better)
metal rod to use as a ring mandrel - I used 1/4 inch metal rod and 3/16 inch brass rod
non-ferrous metal for making rings - I used 17 ga. aluminum wire for electric horse fencing - $22 for 1/4 mile spool of wire.
drill press or hand drill
drill driver to help speed up coiling the wire
small wood dowels or skewers the same size as the coil mandrels.
Wire of your choice: Any non-ferrous (no iron or steel) wire should work, but test a small sample before you coil up tons of rings.
Standard SAFETY warning: be careful when using sharp tools and power tools.