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.
(one of the best sources of calcium), high calcium mineral water can help. Range: There is a huge variance between brands. The waters we sampled had. between 4.5 and 288mg/litre. Best: Acqua Della Madonna (Â£1.59 per 75cl) 288mg/litre; Badoit (79p per. litre) 190mg/litre.