What are some methods for drilling through cast iron?


Quick Answer

To drill through cast iron, use a 135-degree point angle cobalt drill bit, a colored titanium nitride bit or any bit designed to drill metal at a mid-range speed for soft cast iron and at a slow speed for hard cast iron. Proceed slowly to prevent overheating and wearing out the bit. Use a lubricant to prevent the iron from cracking and to prevent the wear on the bit.

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Full Answer

Begin drilling slowly to start the hole. Hold the bit perpendicular to the surface. Stop drilling every few seconds to allow the bit to cool.

If drilling only a few holes, you do not need to use lubricant because cast iron has a high carbon content that acts as a lubricant. Using a lubricant is messy and causes metal fragments to stick to the drill bit. If drilling several holes, using a lubricant helps to keep the drill bit from overheating and prevents it from wearing out. Use a few drops of oil or a water-based lubricant before drilling each hole. Do not use oil if tapping, as the metal debris needs to fall from the bit to prevent it from getting trapped in the threads.

When you've finished drilling all holes, use a round metal file to smooth the edges.

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