Best drill bits for tile: carbide spear and diamond picks for ceramic and porcelain

01What should a drill bit for tile have?

A tile bit needs a cutting edge harder than the glaze, a way to stay on the slippery surface when the hole starts, a shank your drill can hold, and a way to shed heat. Ordinary twist drills and wood bits meet none of these, which is why tile has its own family of bits. Porcelain is the hardest case, and the requirements below are listed with that in mind.

Cutting edge: carbide spear or diamond

Two edge types are sold for tile. A carbide spear-point bit has a spade-shaped carbide point; Wikipedia's drill-bit summary describes these as glass bits that run at low speed and get hot and wear quickly. A diamond bit or diamond hole saw grinds rather than cuts, and Starrett's catalogue lists diamond tile drills and diamond hole saws for porcelain, glass and stone. In the summary of bit types by material, the diamond core bit or diamond hole saw is the entry for ceramic tile, porcelain, glass and stone, with carbide spear points kept for glass. Our drill bits by material hub shows how tile sits beside wood, metal and masonry bits.

Starting control

Tile gives a bit nothing to bite into, so starting is where most holes go wrong. Makers answer this in different ways: Bosch grinds the GT3000 tip to a precision point that it says reduces walking, Bosch's HDG11 set comes with an AutoStart pilot bit, and Diablo says its DHS1500DG needs no pilot bit at all and is started at an angle. A guide jig or tape on the glaze is a common workshop habit, but none of the sources behind this page states it, so it is left as an option rather than a rule.

Cooling

Diamond tile drills and diamond hole saws must always be cooled with water, according to Starrett. DeWalt builds this into the DW5572, which has reverse-spiral threads for continuous water cooling, and Milwaukee tells users to dip its diamond bit in water before each cut.

Shank and drive

Shanks on tile bits vary more than on twist drills: three-flat, straight round, 1/4 in hex and mandrel-mounted designs all appear in the picks below. Match the shank to the chuck or holder you have before choosing on edge type alone.

03Which bit should you use on ceramic and which on porcelain?

Use a diamond bit or diamond hole saw on porcelain, and either a diamond bit or a carbide spear point on glazed ceramic. Porcelain is the material the diamond picks are sold for: DeWalt names solid-body porcelain, Milwaukee names porcelain and hard tile, Bosch names the hardest tiles and hard ceramics, and Diablo names porcelain first in its list. Bosch's spear-point GT3000 is listed for glass and tile in general without naming porcelain.

Two makers go further and say outright that a glass-and-tile bit is the wrong choice for porcelain. Milwaukee states that its carbide ceramic tile and glass bits are not recommended for porcelain tile, and Bosch's tile guidance sends porcelain jobs to its HEX-9 HardCeramic bit rather than to its glass and tile range. A spear point that drills glazed wall tile well is therefore no evidence that it will drill through-body porcelain.

Carbide spear point vs diamond core: what changes?

The spear point cuts with a sharpened carbide edge, and its weakness is heat: it runs hot and wears quickly. The diamond core grinds a ring of material away and needs water throughout. For a few anchor holes in a glazed wall tile, a spear set covers the most sizes in one box. For porcelain floor tile, the diamond bits are the ones whose makers list it.

Small bit vs hole saw: where is the line?

The line is the hole size. Small diamond bits such as the Milwaukee 1/4 in bit make holes for plugs and screws. Pipe, valve and fitting holes need a diamond hole saw such as one from the Bosch HDG11 set or the Diablo DHS1500DG. To size a hole around a steel pipe, read the outside diameter from our page on hole saw sizes for pipe and conduit and allow some clearance.

Which pilot bit goes with a tile hole saw?

A hole saw that uses a pilot needs one that can survive the tile. Milwaukee's standard hole saw pilot bits are 3-1/2 or 4 in long, and for carbide-grit hole saws in ceramic tile, brick and other abrasive materials Milwaukee tells users to fit its carbide-tipped pilot bit instead of the plain one. Diamond saws avoid the question in different ways: Bosch's HDG11 kit includes its own AutoStart pilot, and Diablo's DHS1500DG runs with no pilot at all.

04How fast should you drill tile?

Drill tile slowly. Glass bits are run at low speed, and diamond hole saws have published speed bands that fall as the diameter rises. Starrett's catalogue gives the bands in the table below for its diamond-grit hole saws, always with water cooling. A bigger saw means a lower speed, because the rim travels further on each turn.

The figures are Starrett's for its own saws. Bosch, DeWalt, Diablo and Milwaukee do not publish a speed table on the product pages behind this guide, so use the lower end of Starrett's band as a starting point and the bit maker's own instructions where they exist. One common belief is that tile should be drilled fast to get through the glaze. The sources say the opposite: glass bits are run at low speed, and diamond tile tools need water to carry heat away.

05Should hammer mode be on when you drill tile?

No. Every maker behind this page that addresses it says to drill ceramic tile with the hammer action off: Bosch says to use the rotary setting only, Milwaukee says its tile and glass bits are for drill drivers only, and Makita says its tile bits are for use in a driver-drill. Hammer action is how masonry bits break up concrete; on a glazed tile it cracks the face around the hole instead of cutting it.

The same goes for a combi drill with a hammer collar: set the collar to drill, not to the hammer symbol, before the bit touches the glaze. Once the tile is through and the bit reaches concrete or block behind it, change to a masonry bit and only then switch hammer on.

How should the hole be started?

Start slowly and lightly, then build up. Bosch's tile guidance is to begin the hole at low speed with light pressure and to raise pressure and speed only once the bit has cut into the surface. That matches the reason tile bits skate: until the tip has broken through the glaze it has nothing to hold it, and extra force at that moment pushes it sideways rather than down.

06Can a masonry bit drill tile?

A masonry bit is the wrong first tool for tile. Masonry bits have a brazed carbide tip and are normally used with hammer action in concrete, brick and block, where the tip breaks the material up. Tile calls for a bit that grinds or slices through a hard glaze, which is why the material summary gives it diamond bits and spear points instead.

The two meet when tile is fixed to concrete or block. Drill through the tile with a tile bit, then change to a masonry bit for the substrate behind it. Our carbide masonry bit picks cover that second step, including sizes for anchors.

A rotary hammer is not needed for tile and its bits will not fit an ordinary chuck. SDS-plus bits have a 10 mm slotted shank and SDS-max bits an 18 mm one, and neither system takes a round or hex tile bit directly. Chuck adapters on SDS-plus hammers are for rotation-only drilling with the hammer switched off. The difference between the two hammer systems is set out in our page on SDS-Plus versus SDS-Max.

07Which grinder disc cuts tile when a drill bit is not enough?

For straight cuts, notches and outlet cut-outs in ceramic and porcelain tile, makers point to a continuous-rim diamond blade on an angle grinder, not a drill bit. Unlike the diamond drill bits above, which need water, a blade on an electric grinder is run dry. Blade choice, speed ratings and guards are covered in the tile blades for angle grinders section of the grinder disc guide.

08Why does a tile bit fail early?

Most tile bits fail from heat, from wandering at the start, or from being used on a harder material than they are made for. Each cause points to a different fix.

• Heat from dry drilling. A diamond bit run dry overheats, and spear points get hot and wear quickly even when used correctly. Keep water on the cut and slow down.
• Walking on the glaze. A bit that skates across the surface chips the glaze before the hole starts. Choose a bit with a starting aid, such as a precision spear tip or a pilot bit, or start an unpiloted diamond saw at an angle as Diablo instructs. The causes of bits drifting off the mark are covered in more depth in our page on why bits wander.
• Wrong edge for the tile. A spear point used on porcelain is working outside its maker's stated applications, and Milwaukee says plainly that its glass and tile bits are not for porcelain. Move to a diamond bit.
• Hammer action left on. Bosch, Milwaukee and Makita all limit their tile bits to rotary drilling, so a drill left in hammer mode is being used against the makers' instructions.
• Wrong tool. Bosch lists the HDG11 for impact drill/drivers and Milwaukee's bit has a hex shank, while Bosch lists the GT3000 for rotary drills and drivers and Diablo lists its saw for hand-held drills. Check the maker's tool listing before fitting a bit to an impact driver.
• Bit snapping. Carbide and diamond tools are brittle, so a drill held at an angle can break the bit once the hole has started.

For tools beyond drills, the accessory finder shows the published chuck and holder type for each drill and driver in our fact base, and the buyer guides cover bits for wood, metal and concrete.

09Questions readers ask