How Do You Drill Through Cast Iron?

To drill through cast iron, use a carbide diamond drill bit dipped in lubricating oil to make the hole and finish with a round metal file. Wear all proper safety equipment while drilling through cast iron, including protective eye-wear, goggles and gloves.

  1. Collect the materials
  2. Drilling through cast iron requires the following materials: a variable speed drill, 1/4-inch drill bit, carbide diamond drill bit, small paintbrush, masking tape, permanent marker, round metal file, water and lubricating oil.

  3. Mark the hole
  4. Before starting to drill, cover the intended area with masking tape to keep the drill from skipping while drilling. After placing the masking tape down, use the permanent marker to mark the hole's center and signify where to begin drilling.

  5. Prepare the drill
  6. Use protective eye-wear, a dust mask and gloves while drilling. If drilling through a cast iron sink, the sink has a top layer of ceramic coating that can be drilled with the 1/4-inch drill bit. Place a small amount of lubricating oil on the bit, and keep a bucket of water close by to cool the bit.

  7. Drill the hole
  8. First drill through the ceramic layer with the 1/4-inch porcelain drill bit, starting slowly and keeping the bit vertical to the surface. Once the bit reaches the cast iron, the bit will no longer drill through. Use the small paintbrush to clear away the debris. Then change to the carbide tip, cooling the porcelain tip before removing it. Place a small amount of lubricating oil on the bit and re-lubricate the bit while drilling.

  9. Perform finishing work
  10. After the holes are drilled, smooth the edges with a round metal file.