Tile Drill Bits: Which to Use and How to Drill Without Cracking

Drilling into tile and porcelain is one of the highest-stakes tasks on any bathroom, kitchen, or exterior finishing job. Make a mistake, and you're replacing a cracked tile that's already thin-set and grouted — costing you time, money, and profit margin. These materials are hard, abrasive, and completely unforgiving to impact.

Which Bit for Which Tile?

The bit follows the tile, not the job. Work out what you are drilling into first — if you are not sure whether a floor tile is ceramic or porcelain, look at a cut edge or a broken piece: ceramic usually shows a paler body under the glaze, porcelain is the same colour most of the way through and feels heavier for its size.

If you genuinely cannot tell, use diamond. It works on everything on that list, and the only penalty is cost — carbide is cheaper but it fails on the harder half. The full speed and wet-or-dry breakdown for each bit type is in the summary table at the top of this page.

Why Diamond and Carbide Cut Tile Completely Differently

Carbide-tipped bits work like a miniature chisel — the hardened tip scrapes and shears away material as it spins, the same basic mechanism a masonry bit uses on brick. This works fine on softer ceramic, but modern porcelain is fired at much higher temperatures and is far denser — scraping simply can't keep up, and the carbide tip overheats, dulls, and eventually snaps.

Diamond bits don't cut in the traditional sense. Industrial diamond grit bonded to the bit's edge grinds the material away through friction, the same principle as a grinding wheel. This is why diamond bits work on virtually anything — porcelain, glass, natural stone — but also why they need constant cooling: friction generates heat, and heat is what strips diamonds off the steel matrix.

What PEI Actually Measures

PEI ratings appear on tile boxes and get quoted constantly, but the scale measures surface abrasion resistance — how well the glaze survives foot traffic — not hardness in the sense a drill cares about. PEI 1 is wall tile only; PEI 5 is rated for commercial floors. It is a useful proxy because the tiles built to survive heavy traffic are also the dense ones that defeat carbide, but it is a proxy, not a measurement of what you are about to drill.

The real difference is the body. Porcelain is fired from finer clay at a higher temperature, which vitrifies it — the particles fuse into something close to glass. That is why porcelain absorbs almost no water (under 0.5% by definition) while ordinary ceramic can absorb several percent, and it is why a carbide edge that scrapes ceramic away simply skates and heats on porcelain.

How to Tell a Carbide Bit Has Failed

Carbide does not usually snap without warning. It goes through a stage first, and recognising it saves the tile: the bit stops producing dust and starts producing nothing, the drill note rises, and you find yourself pressing harder to get anywhere. That extra pressure is what cracks the tile — the bit failed a minute earlier, but the damage happens when you compensate for it.

If the tip has gone shiny or slightly blue, it is done. A blunt carbide bit cannot be usefully sharpened at home, and pressing on with it is more expensive than the bit was.

RPM Guide: Two Different Scales

Most guides give you a single RPM number for tile, which is genuinely misleading. Small drill-mounted bits need one range; large diamond core bits need a completely different one that decreases as the bit gets bigger.

By Material (Drill-Mounted Small Bits)

By Diameter (Drill-Mounted Diamond Core Bits)

Counterintuitively, larger core bits need slower RPM — running them too fast glazes over the diamond grit before it can cut.

How to Drill Into Tile Without Cracking It

The bit matters, but technique is what decides whether the tile survives. Most cracked tiles are not the fault of the bit — they come from the bit skating before it bites, from hammer mode, or from pushing too hard at the moment of breakthrough. Six steps, in order.

1. Mark through masking tape

Glaze is hard and glossy, and a bit placed on bare glaze will wander before it cuts. Put a cross of masking tape over the spot and mark on the tape. It gives the tip something to grip for the first few seconds and stops the point sliding off your mark and scoring a scratch across the face of the tile. It also catches the dust. This costs ten seconds and prevents the single most common way people ruin a tile.

2. Start at 45 degrees, then come upright

Do not begin with the drill perpendicular to the tile. Tip it to roughly 45 degrees and let the edge of the bit cut a small crescent through the glaze first. Once that notch exists, the bit has something to sit in, and you can slowly bring the drill up to 90 degrees and carry on. Diamond hole saws in particular have no centre point at all, so without this step they will skid across the surface. If you find the angle awkward, clamp a scrap of plywood with a pilot hole over the tile and use it as a guide.

3. Low speed, and never hammer mode

Check the drill is in rotary mode before it touches the tile. A single pulse of hammer action will crack tile instantly, no matter which bit is fitted — this is the fastest way to destroy a tile that is already on the wall. Keep the speed low: around 600–900 rpm for carbide on ceramic, and slower still for diamond, dropping as the bit gets wider. The speeds are in the chart above.

4. Keep it cool

Heat is what kills bits and cracks tile. Carbide on soft ceramic can be run dry if you pause to let it cool, but diamond on porcelain cannot — run a diamond bit dry for a few seconds and the heat strips the grit off the steel. A spray bottle, a wet sponge held against the tile, or a ring of plumber’s putty holding a small puddle of water all work. On a vertical wall the putty dam is the one that actually stays put.

5. Ease off at breakthrough

The last millimetre is where tiles chip. As the bit is about to come through the back face, there is nothing supporting the glaze around it, so pressure at that moment blows a crater out of the reverse side. Back off and let the bit finish under its own weight. On a wall tile you will not see the back, but the chip weakens the tile around the fixing, which is where cracks start later.

6. Then deal with what is behind the tile

This is the step most guides skip. Getting through the tile is only half the hole. Behind it is plasterboard, cement backer board, plywood or masonry, and that layer usually needs a different bit — a masonry bit if you have hit block or brick, or nothing special at all for plasterboard. Swap bits rather than pushing the tile bit through; a diamond hole saw is not designed to cut timber or block and will glaze over trying.

In a shower or anywhere else that gets wet, seal the hole before anything goes into it. A bead of silicone in the hole and on the fixing keeps water out of the substrate, which is what actually fails in a bathroom — not the tile, but the board behind it once water gets in through a fixing hole.

Can you drill into the grout instead?

Yes, and it is easier — grout is much softer than tile and a masonry bit goes through it without any of the above fuss. Drilling grout also means that if you ever remove the fixing, the hole can be raked out and re-grouted invisibly, where a hole in a tile is permanent.

The trade-off is holding power. Grout lines are narrow, the grout itself is weak compared with the tile body, and the anchor is only gripping a thin joint. That is fine for a lightweight towel ring or a picture. It is not fine for a grab rail, a heavy mirror, or anything someone might put their weight on — those need to go through the tile and into whatever is behind it.

Drill-Mounted vs. Angle-Grinder-Mounted Diamond Bits

Most homeowners only ever use a drill-mounted diamond bit, and for anchor holes and small fixtures, that's the right call — wet electroplated or sintered crowns run cool at low RPM and mount directly in a standard drill chuck.

Professionals doing high-volume work often reach for a completely different setup: dry vacuum-brazed diamond cores mounted on an angle grinder via an M14 thread, spinning at 11,000 to 14,000 RPM. These cut dramatically faster with no water needed, at the cost of requiring a grinder instead of a drill and careful heat management through brief cooling breaks. Note this is for drilling round holes — if you need to cut tile in a straight line instead, that's a different tool and technique covered in our angle grinder buying guide.

Is the Grinder Setup Worth It?

For a homeowner drilling three holes for a shower rail, no. The bits cost several times what a drill-mounted crown costs, you need a grinder with an M14 spindle, and the technique is less forgiving. A wet drill-mounted bit will do the job for a fraction of the outlay.

It becomes worth it at volume, or where water is a problem. A tiler cutting dozens of holes a week gets through them several times faster dry, with no dam to build and no puddle to clean up — and on a finished bathroom wall, not introducing water is itself an advantage.

The safety difference is real and worth stating plainly. A drill at 600 rpm that binds will twist your wrist. A grinder at 14,000 rpm that binds will kick the tool out of your hands, and it is holding an abrasive crown against a glazed surface at head height. Two hands, both of them on the tool, eye protection without exception, and never with the guard removed.

Drilling Thin Large-Format Porcelain Panels

Large-format porcelain slabs — increasingly common for shower walls and countertops — present a problem standard tile doesn't: they're both larger and thinner than conventional tile, which means they flex more under drilling pressure. That flex is what cracks them, not just raw hardness.

The fix is support, not a different bit. Back the panel fully wherever you're drilling — never drill over an unsupported span or near an unsupported edge — and reduce downward pressure even further than you would on standard-thickness tile. Let the diamond grit do the work; on thin panels, pressure is the enemy even more than heat.

How to Support a Panel Properly

Support means the panel cannot flex at the point of the hole, and there are only really three ways to get it. On a bench, lay the whole slab on a flat sheet of ply or MDF rather than across two trestles — the gap between trestles is exactly where slabs snap. On a wall, drill where there is something solid immediately behind: over a stud, a batten, or a fully bedded area of adhesive rather than a void.

The problem is that you usually cannot see the voids. Tap across the area with a knuckle first and listen — a hollow note means the adhesive did not make contact there, and drilling into an unsupported spot is how large-format panels crack even at low pressure. If the spot you need is hollow, that is worth knowing before the bit touches it, not after.

Keep away from edges too. Aim for at least 25mm from any cut edge and more from a factory edge if the layout allows, because an edge has nothing on one side to distribute the stress into.

Carbide Spear-Point Bits

Carbide scrapes through softer ceramic wall tile (PEI 1–3) affordably, and for a handful of fixture holes it is all you need. It will not survive dense porcelain — don't force one past its limit.

Check the tip shape before you buy. A true tile bit has a flat, arrowhead-shaped carbide tip — a spear point. A masonry bit has a blunter, angled tip designed to pulverise brick, and while it will get through soft ceramic, it is more likely to chip the glaze on the way in. Packaging that says Glass and Tile is the reliable signal.

Installing a Carbide Spear-Point Bit

1. Place a piece of masking tape over your mark — this gives the bit grip so it doesn't skate across the glaze.
2. Start the drill at low speed with the bit at a slight angle to score the surface, then bring it to 90 degrees once it's biting in.
3. Increase speed only after the bit has penetrated the glaze. Let the bit do the work — added pressure cracks tile, it doesn't speed up the cut.

Tile Hole Saws: Diamond Bits for Pipes and Large Cut-Outs

Diamond bits are the only reliable option for porcelain, glass, and natural stone. Keep the bit wet or use frequent cooling breaks — heat is what destroys diamond bits, not the material itself.

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Cutting a Hole in Tile That Is Already on the Wall

Almost every guide assumes the tile is loose on a bench, where you can clamp a guide over it and a puddle of water sits where you put it. On a wall that is already tiled and grouted, neither is true, and it is the harder job by some distance.

Three things change. A water dam has to be built from plumber’s putty pressed into a ring, because anything else simply runs down the wall. The bit wants to walk downward under its own weight, so the 45-degree start matters more, not less. And you cannot see the back face, so you have no warning before breakthrough — go by feel and ease off as soon as the resistance drops.

If the cut-out is large and the fixture will cover it, a guide made from a scrap of plywood with the right size hole already cut, taped firmly to the wall, is worth the five minutes it takes. It holds the saw square and stops it wandering across the glaze while the groove is still shallow.

When the Hole Crosses a Grout Line

Large cut-outs often land on a joint rather than in the middle of a tile, and that is where they crack. The grout is softer than the tile either side of it, so the bit cuts through it faster, snatches, and the sudden change in resistance twists the saw. That twist is what breaks the tile edge.

If you have any choice in the position, move the hole so it sits within one tile. If you do not — and with a mixer valve you usually do not — slow right down as the rim reaches the joint, keep the pressure light and constant, and let the saw grind rather than pushing it through the soft strip. Cutting wet helps here more than anywhere else, because it stops the bit grabbing.

Installing a Diamond Hole Saw

1. Build a small water dam around your mark with plumber's putty, or have someone spray the bit continuously with water on vertical surfaces.
2. Start at a 45-degree angle to let the diamond grit bite into the glaze and create a shallow groove, then slowly tilt to 90 degrees.
3. Keep speed moderate and let the bit grind through — pulling it out periodically to clear debris and dissipate heat extends bit life significantly.

Large-Diameter Rough-Ins and Plumbing Cutouts

Small anchor holes are one thing — installing a showerhead, mixing valve, or running PVC through a tiled wall means stepping into much larger diameters. For a standard shower arm, a 1/2-inch or 5/8-inch diamond bit is typical. For mixing valves, you'll generally reach for a 1-3/8-inch or 2-inch diamond core bit. A set that spans this full range saves buying individual bits one size at a time.

Cut the hole slightly larger than the pipe, not a tight fit. Tile is brittle and a building moves. If the pipe is clamped hard against the edge of the hole, any movement of the fixture loads the tile directly and it cracks from the hole outward. A few millimetres of clearance all round, hidden by the escutcheon or flange, is what stops that.

Common Mistakes to Avoid

Frequently Asked Questions

Related Guides

• Drill Bits for Glass — The same diamond bits work on both, but glass needs even lower speed.
• Drill Speed by Material — RPM for wood, metal and masonry, not just the brittle materials.
• Drill Bit Materials Explained — What HSS, cobalt and carbide actually mean, and when each is worth paying for.
• Masonry vs Concrete Bits — For when you are through the tile and into the wall behind it.
• Why Drill Bits Burn or Break — What the blue and black marks on a spent tip are telling you.
• Drill Bit Size Chart — Answer three questions and get the bit, the size and the speed for your job.