Go to a hardware store and get the size bit you need that is made for metal. Most cast iron isn't really hard unless it is white cast iron. If the hole is over 3/16, pre-drill it with a small bit first. It might be a good idea to use some cutting oil to.
Other foods that are high in calcium include: 1  Spinach. 2  Kale. 3  Okra. Collards. 4  Soybeans. White beans.  Some fish, like sardines, salmon, perch, and rainbow 1  trout. Foods that are calcium-fortified, such as some orange juice, oatmeal, and breakfast  cereal.
1 Milk, yogurt, and cheese are the main food sources of calcium for the majority of people in the United States. 2  Kale, broccoli, and Chinese cabbage are fine vegetable sources of calcium. 3  Fish with soft bones that you eat, such as canned sardines and salmon, are fine animal sources of calcium.