Which drill bit should I use for porcelain tile?
Which drill bit should I use for porcelain tile?
A diamond core bit, cooled with water, at low speed — carbide spear points do not cut porcelain.
Porcelain is fired to near-vitrification, so it is denser and much harder than ordinary ceramic wall tile — hard enough that tungsten carbide barely scratches it and only diamond abrades it at a useful rate. That difference is why so many people arrive at this question having already destroyed two tile bits. Diamond cutting is a grinding process, and grinding generates heat that both cracks the tile and burns the bond holding the diamonds on, so water is doing two jobs: cooling and flushing away the swarf that would otherwise glaze the rim. Starting is the other difficulty, since a core has no point: tilt the bit to cut a crescent first, then bring it upright once it has a groove to run in.
The options, ranked
| Option | Good at | Bad at |
|---|---|---|
| Diamond core bit | The only reliable option: a sintered or vacuum-brazed diamond rim grinds through vitrified porcelain and natural stone. | Needs constant cooling and low speed, and is ruined by running dry. |
| Wet diamond core with a guide jig | The suction or spring jig holds the core on the mark and holds a small reservoir of water — the professional setup. | Another thing to buy for a job that may be one hole. |
| Carbide spear point | Fine on ordinary glazed ceramic. | Blunts within seconds on porcelain and polishes the surface without cutting. |
Technique that changes the outcome
- Low speed, no hammer, and never let the rim run dry
- Start at an angle to cut a groove, then bring the core upright
- Build a plasticine dam around the mark and fill it with water, or use a jig with a reservoir
- Lift every few seconds to let water back into the cut
- Ease off at breakthrough so the core does not snatch and chip the back of the tile
What goes wrong
- Dry-drilling porcelain, which kills the bit and produces respirable silica dust
- Any hammer action
- Pressing harder when it slows — that is heat, not lack of force
Compiled practical guidance rather than a published standard. Product formulations vary by brand and market, so read the label — and where the work is structural, electrical or gas, the regulations that apply where you are govern rather than anything here.
Other drill bit questions
| For | Use |
|---|---|
| Tile | A spear-point carbide or diamond bit in rotary mode only — hammer action shatters tile, every time. |
| Metal | An HSS twist drill, ideally with a 135° split point, run slowly with firm pressure and cutting fluid. |
| Concrete | An SDS-plus carbide bit in a rotary hammer — a normal hammer drill will get there eventually and blunt several bits doing it. |
| Masonry | A carbide-tipped masonry bit in hammer mode for brick and block; step up to an SDS rotary hammer above about 10 mm. |
| Stainless steel | A cobalt bit at low speed with heavy constant pressure and cutting fluid — and never let it stop cutting. |
| Wood | A brad point bit for clean holes up to about 13 mm; an auger for depth and a Forstner for a flat bottom. |
| Plasterboard (drywall) | Almost none — an ordinary HSS or brad point bit in rotary mode, and the real question is which fixing goes in the hole. |
| Glass | A spear-point carbide or a diamond bit, run slowly under water — and toughened glass cannot be drilled at all. |
| Plastic | An HSS bit ground to a shallower rake, or a plastic-specific bit, at low speed with a backing board — acrylic especially will crack. |
| Hardened steel | Solid carbide in a rigid setup, or soften the spot first — HSS and cobalt cannot cut anything much above 50 HRC. |
| Aluminium | A sharp HSS bit at high speed with a wax or paraffin lubricant — the problem is aluminium sticking to the bit, not hardness. |
| Large holes in wood | Spade for speed and roughness, auger for depth, Forstner for a clean flat bottom, hole saw for big diameters in thin stock. |
Common questions
- Which drill bit should I use for porcelain tile?
- A diamond core bit, cooled with water, at low speed — carbide spear points do not cut porcelain.
- What should I avoid?
- Dry-drilling porcelain, which kills the bit and produces respirable silica dust Any hammer action Pressing harder when it slows — that is heat, not lack of force
Related pages
- Which drill bit should I use for tile? A spear-point carbide or diamond bit in rotary mode only — hammer action shatters tile, every time.
- Which drill bit should I use for metal? An HSS twist drill, ideally with a 135° split point, run slowly with firm pressure and cutting fluid.
- Which drill bit should I use for concrete? An SDS-plus carbide bit in a rotary hammer — a normal hammer drill will get there eventually and blunt several bits doing it.
- Which drill bit should I use for masonry? A carbide-tipped masonry bit in hammer mode for brick and block; step up to an SDS rotary hammer above about 10 mm.
- Which drill bit should I use for stainless steel? A cobalt bit at low speed with heavy constant pressure and cutting fluid — and never let it stop cutting.
- Which drill bit should I use for wood? A brad point bit for clean holes up to about 13 mm; an auger for depth and a Forstner for a flat bottom.
- Which drill bit should I use for plasterboard? Almost none — an ordinary HSS or brad point bit in rotary mode, and the real question is which fixing goes in the hole.
- Which drill bit should I use for glass? A spear-point carbide or a diamond bit, run slowly under water — and toughened glass cannot be drilled at all.
- Which drill bit should I use for plastic? An HSS bit ground to a shallower rake, or a plastic-specific bit, at low speed with a backing board — acrylic especially will crack.
- Which drill bit will go through hardened steel? Solid carbide in a rigid setup, or soften the spot first — HSS and cobalt cannot cut anything much above 50 HRC.
Sources
- Typical range compiled from manufacturer specifications — At One Place