How to Drill a Hole Into a Cast Iron Sink

white bathroom sink set into a light wood countertop
What You'll Need
Cast iron sink
Permanent marker
Masking tape
Variable speed drill
¼" drill bit
Small paintbrush
Carbide diamond bit
Round metal file
Lubricating oil or container of water

For the homeowner who wants a heavy and durable sink, you can't beat a cast iron sink. In addition to its durability, this sink typically comes with a ceramic coating that gives you not only a smooth finish but a colored one that will match your other kitchen appliances or bathroom fixtures. If there is a disadvantage to these sinks it is that adding special fittings like spray hoses can be a major challenge if the fitting requires a hole to be drilled through the sink surface. But if you have the right tools and technique it may not be beyond your capabilities. Here's how to drill your hole:

Step 1 - Locate the Hole

If you're cutting a hole for a faucet, your hole will probably be located in the center of the sink's rear surface. For faucet knobs, each hole will be positioned on the opposite side from the other knob, each placed about three inches out from the faucet. Identify the spot where you want your holes, stick a small piece of masking tape on that spot. It will keep the drill bit from skipping across the sink's surface when you begin to drill. Finally, use your permanent marker to place a dot on the making tape.

Step 2 - Prepare to Drill

a cordless drill

Insert your porcelain bit into your drill chuck and tighten the chuck. Be sure it is tight. Place a drop of oil on the tip end of your bit to keep the friction from burning it when you begin drilling. If you don't have lubricating oil, have a container of cool water handy to dip the bit in when it becomes hot as you drill. Finally, wear goggles or other glasses to protect your eyes from flying bits of metal.

Step 3 - Drill Your Hole

man wearing tool belt and holding a drill

Begin drilling slowly with the point of your porcelain bit on the dot you marked on the masking tape. Hold the drill so that the bit is as nearly vertical as possible while it is turning. The first bit will drill through the porcelain only. Then, it will stop making a hole when it comes to the iron. At that point, you'll need to stop the drill and remove the porcelain fiber debris with your paintbrush. Replace the bit with the carbide drill bit, but in doing so be sure you cool the porcelain bit before removing it. Then, begin drilling again as you did with the first bit. Continue drilling, stopping every few seconds to cool your bit with lubricating oil, or dip your bit into the water from the water container. Be careful when doing this that you do not touch the hot bit. Continue with this process until you have drilled through the cast iron.

Step 4 - Finish

When you have drilled your first hole and you need to drill others, use the same process and the same bits. When finished with making your holes, use a round metal file to smooth the edges of the holes you made.