Drill Bit Material Chart: HSS, Cobalt, Carbide & Coatings

There are two completely different questions hiding inside the phrase “drill bit material”. One is what the bit is made of. The other is what you are drilling into. This guide answers the first one properly, then maps it onto the second.

Most guides skip straight to a list of bit shapes and never explain the metallurgy, which is why so many people buy a titanium-coated set, hit a piece of stainless, and watch it die in four holes. The bit was not defective. It was the wrong alloy for the temperature at the cutting edge, and that single idea explains almost every drill bit failure on a job site.

What drill bits are actually made of

Nearly every drill bit sold for handheld use starts life as high-speed steel — a tool steel alloyed with tungsten, molybdenum, chromium and vanadium. From that base, manufacturers do one of three things: leave it alone, add cobalt to the alloy, or abandon steel entirely for tungsten carbide or industrial diamond.

Two properties matter more than anything else printed on the packaging.

• Alloy composition. This is the material through the whole body of the bit. Cobalt content is the usual lever: roughly 5% for M35, roughly 8% for M42. Because cobalt is part of the alloy rather than a surface treatment, it is still there after the bit is sharpened.
• Point angle. General-purpose bits use a 118° point, which suits wood and soft plastics. Metalworking bits use a flatter 135° split point that stops the bit skating across a smooth surface, which is why you can start a hole in steel without a centre punch.

The material ladder, and why hardest is not best

Rank the four families by hardness and you get a clean ladder: high-speed steel in the low 60s HRC, cobalt HSS in the high 60s, tungsten carbide around 82 HRC, and diamond off the top of the scale entirely.

That ladder is genuinely useful, and it is also a trap. Hardness measures resistance to being scratched or indented. It says nothing about what happens when the bit gets levered sideways in a hole. Toughness — the ability to absorb force and flex instead of fracturing — runs in the opposite direction. Cobalt HSS will bend a noticeable amount under side load and spring back. Tungsten carbide, at the same moment, snaps.

This is why the honest answer to “what is the strongest drill bit material” is carbide, and why carbide is the wrong choice for most handheld drilling. In a hand-held drill your hand is never perfectly steady, and every wobble is side load. Carbide belongs where the tool is rigid, or where the cutting action is percussive rather than rotary, which is exactly why it dominates masonry bits and disappears from general metalwork.

M2 vs M35 vs M42: what the cobalt actually buys you

The grades stamped on a bit box are the most useful and least explained thing about it. All three are high-speed steel. The difference is cobalt content, and what cobalt buys is not hardness at room temperature — it is red hardness, the temperature at which the steel stops holding a cutting edge.

That matters because a drill bit destroys itself with heat, not with force. Friction at the cutting lip generates heat that either escapes into the chip and the workpiece, or stays at the edge. What stays at the edge is what kills the bit. Once the steel passes its red-hardness limit, the edge softens, stops cutting, starts rubbing, and work-hardens the material underneath it.

Read the chart and the buying decision makes itself. M2’s limit sits above the mild-steel band, so for mild steel, aluminium and brass it is genuinely sufficient — specifying cobalt there is paying for headroom you will never use. Move to stainless and M2’s line falls inside the band, which is precisely why an HSS bit dies in a few holes in 304. Move to hardened alloys and even M35 runs out.

Two practical notes the spec sheets leave out. First, the extra cobalt that buys heat resistance also makes the bit more brittle, so M42 punishes a sloppy, flexing setup more than M35 does — in a hand drill on awkward work, M35 is often the better real-world choice even when M42 is technically superior. Second, there is a ceiling: once the workpiece itself is harder than roughly 45 HRC, no grade of high-speed steel will cut it well and you need solid carbide.

You may also see M7 on budget cobalt bits. It sits between M2 and M35 in performance and is generally a cost-reduction grade rather than an upgrade — if you are choosing between M7 and M35 for stainless, M35 is the one worth paying for.

Coatings vs core: the titanium misunderstanding

This is the single most misunderstood thing in the entire category, so it is worth being blunt about it: a titanium drill bit is not made of titanium. It is an ordinary high-speed steel bit with a titanium nitride coating a few microns thick sprayed onto the outside. The gold colour is the coating.

That coating is genuinely useful. It is harder than the steel underneath, it reduces friction, and it meaningfully extends bit life in mild steel and aluminium. What it does not do is change the bit’s core. The steel underneath is still M2, still with M2’s red-hardness limit, and once the coating is breached the bit behaves exactly like the uncoated bit it always was.

The consequence is the part almost nobody mentions at the point of sale: sharpening a coated bit removes the coating exactly where it was doing the work. You grind the cutting lip, the lip is where the coating mattered, and now it is gone. A resharpened titanium-coated bit is a plain HSS bit with gold flanks. A resharpened cobalt bit is still a cobalt bit, because the cobalt goes all the way through.

Here is how the common surface treatments actually compare.

So when the question is black oxide vs titanium: black oxide is mostly about rust and storage, titanium nitride is mostly about friction and wear in soft material, and neither one turns a mild-steel bit into a stainless-steel bit. If the job is stainless, you are not choosing a coating — you are choosing an alloy. That is a genuinely different purchase, and it is covered in more depth in our comparison of titanium vs cobalt drill bits.

Which bit material for which job

Everything above collapses into one table once you know what you are drilling.

Each of those rows has a full guide behind it: drill bits for wood, drill bits for steel and metal, masonry drill bits, and drill bits for tile.

Types of drill bits by shape

Material is one axis. Shape is the other, and they are independent — a brad-point bit and a twist bit can be the same M2 steel, ground differently for different jobs.

Twist bit

The default. Helical flutes lift chips out of the hole as it cuts. Works in wood, metal and plastic, which is why it is the shape in every general-purpose index set. Practical limit is around 1 inch in diameter before weight and heat make it impractical.

Brad-point bit

A twist bit with a sharp centre spur and raised outer lips. The spur pins the bit so it cannot wander, and the outer lips slice the wood fibres before the centre clears the waste, which is what produces a clean rim instead of a torn one. Wood only — the fine spur will not survive metal.

Spade bit

A flat paddle with a pointed centre. Cheap, fast, and rough. The right tool for boring 3/4 inch to 1-1/2 inch holes through framing lumber for cable runs, and the wrong tool anywhere the hole will be visible.

Auger bit

A screw tip that pulls the bit through the work, with deep flutes that clear heavy chips. For deep holes in thick timber, where a spade bit would bind and stall.

Forstner bit

Cuts a flat-bottomed hole with clean walls, guided by its rim rather than its centre. The standard choice for European cabinet hinge cups. Wants low RPM and a rigid setup, ideally a drill press.

Masonry bit

A carbide tip brazed onto a steel body, with a blunt chisel-shaped point. It does not cut — it crushes. Pairs with hammer action, and comes in plain round shank for hammer drills or SDS-plus and SDS-max shanks for rotary hammers.

Step bit

A cone of increasing diameters. Drills a range of hole sizes in thin sheet material with one bit, and deburrs as it steps through. Sheet metal and electrical enclosures, not thick stock.

Hole saw

A toothed cylinder that cuts the perimeter and leaves a plug. Used for large-diameter holes — door hardware, pipe penetrations, recessed lighting. Bi-metal versions handle wood and light metal; carbide-tipped ones handle tile and board.

Countersink

Cuts the conical recess that lets a flat-head screw sit flush. Often combined with a pilot drill in one body so the pilot hole and the countersink happen in a single plunge.

Speed and cutting oil

The right bit material still fails if you run it wrong, and running too fast is the most common way to destroy a bit in any material. Speed generates heat, heat kills the edge, and the ladder above becomes irrelevant.

The rule of thumb runs opposite to intuition: the larger the bit, the slower the speed. A large bit’s outer edge travels much further per revolution than a small one, so the same RPM means far higher surface speed and far more heat. Our drill bit speed chart has the actual numbers by diameter and material.

On metal, use cutting oil. It is not optional and it is not just lubrication — it carries heat out of the cut, which is the whole battle. Stainless in particular work-hardens: if you let the bit spin without cutting, the surface under it becomes harder than what you started with, and the hole gets more difficult every second you hesitate. Steady pressure, low speed, never let it rub.

Common mistakes

Frequently asked questions

What is the best drill bit material?

There is no single best one — it depends on heat. M2 high-speed steel is sufficient for wood, aluminium and mild steel. M35 or M42 cobalt is the right answer for stainless and cast iron. Carbide is required for masonry and for hardened steel above about 45 HRC. Diamond is for tile, porcelain and glass.

What is the strongest drill bit material?

Tungsten carbide is the hardest material in common drill bits at roughly 82 HRC, with industrial diamond harder still. But carbide is brittle and fractures under side load, so it is not the best choice for hand-held drilling. For most jobs the strongest usable bit is M42 cobalt at 67–69 HRC.

What is the best drill bit material for metal?

M42 cobalt for stainless, cast iron and hardened alloys. M2 high-speed steel with a 135° split point is enough for mild steel and aluminium, and cobalt there is money you do not need to spend.

What are drill bits made of?

Most are high-speed steel, a tool steel alloyed with tungsten, molybdenum, chromium and vanadium. Higher grades add 5–8% cobalt. Masonry bits use a tungsten carbide tip brazed to a steel body, and tile bits use industrial diamond bonded to a steel core.

Are titanium drill bits actually titanium?

No. They are high-speed steel bits with a titanium nitride coating a few microns thick. The coating reduces friction and extends life in soft metals, but the core is ordinary HSS and the coating is removed from the cutting edge the first time the bit is sharpened.

What is the difference between M35 and M42 drill bits?

Cobalt content. M35 contains about 5% cobalt and holds its edge to roughly 650 °C; M42 contains about 8% and holds to roughly 700 °C. M42 is harder and lasts longer in hard alloys, but it is also more brittle, so M35 often performs better in a hand drill on flexing work.

Is black oxide better than titanium coated?

They do different jobs. Black oxide is a surface conversion that resists corrosion and holds a little lubricant. Titanium nitride is a harder ceramic coating that lowers friction and extends life in soft metals. Neither changes the steel underneath, so neither makes a bit suitable for stainless.

Can you sharpen a coated drill bit?

You can, but you remove the coating at the cutting lip, which is the only place it was doing useful work. After sharpening, a coated bit performs like an uncoated one. Cobalt bits do not have this problem because the cobalt is part of the alloy throughout.

Quick reference

The short version

Cobalt is an alloy and coatings are a skin. That one distinction resolves most of the confusion in this category: cobalt survives sharpening because it goes all the way through, coatings do not because they are microns thick on the outside. Everything else follows from heat — pick the grade whose red-hardness limit clears the temperature your workpiece will generate, run it slow enough to stay under that limit, and keep oil in the cut.

Related guides

• Titanium vs Cobalt Drill Bits: Which Is Actually Better?
• Best Drill Bits for Steel and Metal: Cobalt vs Titanium vs HSS
• Best Drill Bits for Wood: Brad-Point, Forstner & Spade Bits Compared
• Best Masonry Drill Bits: Selection, Technique & Top Picks
• Drill Bit for Tile: Diamond vs Carbide, and How to Drill Without Cracking It
• Drill Bit Speed Chart: Correct RPM for Steel, Wood, Concrete & Tile
• Why Drill Bits Burn or Break (And How to Stop It Happening)
• Drill Bit Size for Concrete Anchors: Chart for All 6 Types