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.
6 of 7. #5: Milk. Last, but probably the most obvious source of calcium, is milk. 8 oz of non-fat milk will give you 299 mg of calcium and 30% of your daily value. 7 of 7. #6: Other non-dairy sources. Other non-dairy sources high in calcium include Chinese cabbage, kale, broccoli, tofu, and salmon.