Cast Iron is often a misunderstood metal, there are plenty of misconceptions about what you can and cannot do with cast iron, most commonly around welding cast iron. But today we are talking about drilling cast iron and the dos and don’ts to achieve a good.
Cast iron may be brittle, but among other metals, it isn’t exceptionally tough, making drilling holes into it a manageable task if you have the tools and knowhow. The good news is, that you don’t need to be overly selective about your choice of drill bit; any metal drill bit will suffice. The key lies in patience to prevent your drill bit from overheating and premature wear.
Cast iron contains a substantial amount of carbon, which acts as a natural lubricant, often allowing for drilling without additional lubrication. Using additional lubricant can be messy and may hinder the removal of metal debris as you drill. On the flip side, a lubricant, whether it’s oil or water-based, helps to cool both the drill bit and the metal, reducing the risk of cracking and excessive bit wear. For the occasional drilling of one or two holes, relying on the material’s inherent lubrication may be sufficient, but if you have a series of holes to drill, using a few drops of cutting oil or spray lubricant before each drill can extend the life of your bit.
Cast iron doesn’t offer much resistance to the rotational force of a drill bit, allowing you to easily penetrate it. The primary concern, however, is dealing with the resulting debris.
Black oxide drill bits are known for their durability and will leave fewer metal shavings from the cast iron when you are finished. If you can use a black oxide drill bit when drilling cast iron, you will experience a more efficient drilling experience.
Alternatively, you can opt for a cobalt steel drill bit, which offers added toughness. Breaking a cobalt steel twist bit while drilling into cast iron is nearly impossible!