Q&A / 

Drilling Ceramic Tile

DEAR TIM: Drilling into ceramic tile just became a priority. My wife wants me to install several new towel bars and other accessories in an older bathroom. I also need to install anchors for a new shower door. I tried drilling into the tile, but got nowhere fast. The drill bit smoked and turned cherry red. I need to get this job done before my wife comes back from her business trip. Help me Tim, you are my only hope. Jonathon O., Los Angeles, CA

DEAR JONATHON: Buddy, you are going to owe me big time. I am going to make you look like a home-improvement super hero. But to do so, you might have to buy a new drill and a few special drill bits.

Ceramic tile is actually artificial or man-made rock. Any geologist will tell you that some rocks are far harder than others. The same is true for ceramic tile. Some tile, especially real porcelain tile, is very hard. You might have tried to drill a hole in porcelain with the wrong drill bit and a drill that spun too fast.

Drilling ceramic tile requires a sharp carbide or diamond drill bit, a slow drill speed and a steady hand. PHOTO CREDIT: Tim Carter

Drilling ceramic tile requires a sharp carbide or diamond drill bit, a slow drill speed and a steady hand. PHOTO CREDIT: Tim Carter

Porcelain tile is hard for several reasons. First, it often has a higher silica content than ordinary tile that is clay-based. Furthermore, porcelain tile is often fired hotter and longer in the kiln. This heating process modifies the chemistry and crystallography of the raw material which transform a putty-like material into artificial stone. The high silica content of porcelain tile also makes it nearly impossible to cut with a snapper-type tile cutter. The tile often shatters with conchoidal fractures like glass.

Many common ceramic tiles are made primarily with clay, but then coated with a thin glaze that is primarily silica. In the kiln, this silica coating turns into a hard, thin glass coating and the clay transform into a low-grade slate-like rock. Once a drill bit penetrates the thin glass coating, it usually drills rapidly through the inner core of regular ceramic tile.

The key to drilling regular ceramic tile is to use a brand-new carbide-tipped masonry drill bit and a drill that has a variable-speed trigger. You never want to drill ceramic tile with the drill at high speed. The lowest speed possible, say 100 or 200 revolutions per minute, is perfect to drill standard ceramic tile. Never use a hammer drill for ceramic tile. You will shatter or crack a ceramic tile if you drill using the hammer function. Hammer drills are fine for brick or concrete, but not ceramic tile.

The biggest mistake you can make when first starting to drill into a tile is applying too much pressure. The drill bit can slip on the highly-polished glazed-tile surface, and the bit will slide possibly creating an ugly scratch. I always placed a piece of duct tape over the spot where I want to drill. I then marked the hole center point on the tape, and begin to drill. The tape does a good job of controlling a wandering drill bit, and it offers scratch protection should the bit slide.

Your drill bit turned red because you were drilling too fast. This creates enormous friction which causes rapid heat build up. Slow drill speeds do not create as much heat. You can keep the drill bit cool by dipping it in a small container of fresh cutting oil every 15 - 30 seconds. After dipping the bit in the oil for a few seconds, wipe the bit off with an old rag to keep the tile and grout oil-free. You can buy this special oil at a plumbing supply house. Plumbers use it to keep pipe-threading dies cool.

If you do have to drill porcelain tile, buy special drill bits that have diamond tips. These bits must also be kept cool with cutting oil, and you must drill slowly to minimize heat buildup. Once the drill bit starts to cut a cone-shaped hole into the tile, the drill will make good progress.

Large holes in ceramic tile can be created any number of ways. You can purchase hole saws that have diamond-cutting surfaces. To drill into existing tile, the hole saw must be equipped with a pilot bit that drills a smaller hole into the center of the larger hole. This pilot bit keeps the larger bit from wandering.

If you have to drill a tile that has not been installed and don't have the tools nor inclination to drill the large hole, take it to a shop that fabricates granite or marble countertops. They have all of the bits and equipment to drill any sized hole.

I used a service like this to drill holes into three pieces of granite tile for my daughter's bathroom. To ensure the holes were drilled in the right places, I covered the face of the granite tile completely with wide masking tape. I then drew the perfect circles in the right locations on each piece of granite. The fabricators did a fantastic job of drilling the holes and all worked perfectly when I installed the granite.

Author's Note:

In a Reader's Comment, Mark asked about drilling a 1/2 hole in his kitchen sink for a water dispenser. His sink is porcelain with cast iron underneath.

Gregg W. of Stevens Point, WI, emailed a helpful answer to Mark's question.

"Just happened to see your answer regarding drilling through a porcelain/cast sink to provide a faucet hole.

I've had considerable experience with all types of cast iron in an industrial setting. It isn't hard to drill or tricky but bits do tend to wander in cast if not held rigidly.

My suggestion would be to start with a masonry bit as in drilling tile and then switch to a normal HSS bit after it is obvious you're through the surface. Use the tape trick. I drilled the hole for, and installed a filter tap hole, this way first time without any problems. I used a 3/4 HSS bit with a 3/8" shank. A hole saw might wander far and wide on this surface. Pilots for hole saws are usually HSS and not the best at that."

Column 674


2 Responses to Drilling Ceramic Tile

  1. Good tips on drilling holes in ceramic tile but how do I cut a hole in the wall large enough to recess a new outlet box? I'm guessing a cutting wheel of some kind. Would one of the rotozip bits work?

Leave a Reply

Your email address will not be published. Required fields are marked *