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.
For more info, see the section on calcium absorption. High calcium foods include dark leafy greens, cheese, low-fat milk and yogurt, bok choy, fortified tofu, okra, broccoli, green beans, almonds, and fish canned with their bones. The daily value (DV) for calcium is 1000mg.
The best way to get more calcium is from your diet. You probably already know that dairy products -- such as milk, cheese, and yogurt -- provide calcium. Other foods that are high in calcium include: 1  Spinach. 2  Kale. 3  Okra. 4  Collards. 5  Soybeans.6  White beans. 7  Some fish, like sardines, salmon, perch, and rainbow trout.ther foods that are high in calcium include: 1  Spinach. 2  Kale. 3  Okra. 4  Collards. 5  Soybeans. 6  White beans. 7  Some fish, like sardines, salmon, perch, and rainbow trout.