Drilling into hardened steel is the ultimate test for any drill bit — the material’s high Rockwell rating can turn an ordinary HSS bit into a dull, smoking stub in seconds. The difference between a clean hole and a broken bit comes down to cobalt content, tip geometry, and the coating’s ability to shed heat at high friction.
I’m Mo Maruf — the founder and writer behind The Tools Trunk. I’ve analyzed metallurgical compositions, coating technologies, and point geometries across dozens of bit sets to isolate what actually withstands the shear forces of hardened steel drilling.
The right bit must maintain edge hardness above 65 HRC while its flute design evacuates hot chips before they weld to the cutting edge. This guide covers the most reliable options currently available so you can pick a drill bit for hardened steel that won’t leave you stranded mid-project.
How To Choose The Best Drill Bit For Hardened Steel
Selecting a bit for hardened steel means ignoring marketing claims and focusing on three measurable attributes: the alloy’s cobalt percentage, the tip’s split-point geometry, and the coating’s oxidation temperature. Bits that lack any one of these three will fail prematurely when the work material exceeds 45 HRC.
Cobalt Content and Material Hardness
Standard HSS bits top out around 60-62 HRC — fine for mild steel but useless against hardened alloys that can reach 65-70 HRC. M35 cobalt steel incorporates 5% cobalt into the matrix, allowing the bit to maintain cutting hardness even when friction heat softens conventional HSS. The cobalt also improves red hardness, meaning the bit stays sharp at high rotational speeds where plain HSS would anneal and go dull immediately.
Point Geometry and Self-Centering
A 135-degree split point is the standard for hardened steel because it reduces the contact area at the tip, requiring less thrust force to initiate the cut. The split creates a secondary cutting edge that breaks chips into smaller pieces, preventing them from binding in the flutes. This geometry also eliminates the need for a center punch on many surfaces, as the tip bites immediately without walking.
Coating Technology for Heat Resistance
Titanium Nitride (TiN) is the entry-level coating, offering hardness around 80 HRC and oxidation resistance up to 1100°F. Titanium Aluminum Nitride (TiAlN) is a step up — it forms an aluminum oxide layer at high temperatures that actually increases surface hardness beyond 89 HRC and protects the bit up to 1500°F. For repeated hardened steel drilling, TiAlN-coated cobalt bits dramatically outlast TiN equivalents.
Quick Comparison
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| Model | Category | Best For | Key Spec | Amazon |
|---|---|---|---|---|
| toolant Cobalt Pro 21pc | Cobalt / TiAlN | Hardened steel & stainless | TiAlN coating, 89 HRC surface | Amazon |
| DEWALT DW1369 29pc | TiN Pilot Point | Versatile job site drilling | Pilot point, 29-piece range | Amazon |
| BOYOUYS M35 Step Set | Cobalt Step Bit | Sheet metal step holes | 4-flute, TiAlN, 1/4-1 inch | Amazon |
| WildBossy M35 20pc | M35 Cobalt | Budget general metal drilling | 135° split, 3-flat shank | Amazon |
| WildBossy M35 Metric 19pc | M35 Metric | Metric fastener drilling | Gold oxide, 1-10mm range | Amazon |
| Milwaukee 48-89-4630 15pc | TiN Shockwave | Impact driver compatibility | 3-flute, TiN, split point | Amazon |
| HIGHFIRE Hex Shank 22pc | HSS Hex Shank | Impact driver metal work | Hex shank, no-spin design | Amazon |
In‑Depth Reviews
1. toolant Cobalt Drill Bit Set Pro 21pc
The toolant Pro set combines M35 cobalt steel with a Titanium Aluminum Nitride coating that reaches 89 HRC surface hardness — a full 9 points higher than standard TiN coatings. This makes it the only set in its price range that can sustain repeated plunges into hardened steel without edge degradation. The bullet point tip is a pilot-point variant that self-centers aggressively, reducing walking even on convex or uneven surfaces.
Each of the 21 bits includes a 3-flat shank that prevents rotation in the chuck under heavy torque — a critical feature when drilling through 60 HRC materials where binding is common. The size range covers 1/16-inch up to 1/2-inch with duplicates on the most-used smaller diameters, which matches real-world wear patterns where 1/8-inch and 3/32-inch bits take the most abuse.
Field reviews consistently report that these bits stay sharp after dozens of holes in stainless and tool steel, with one user noting the set survived drilling through a hardened grid even after snapping a bit under lateral stress — and the warranty replaced the entire set. For anyone drilling hardened alloys regularly, the TiAlN layer and cobalt substrate produce a noticeable lifespan advantage over TiN-only competitors.
What works
- TiAlN coating resists oxidation up to 1500°F, far above TiN limits
- Bullet point tip centers instantly on curved or uneven metal
- 3-flat shank prevents slippage under high torque loads
What doesn’t
- Only one of each larger bit size — replace individually when worn
- Case is molded plastic with no bit size markings on individual slots
2. DEWALT DW1369 Titanium Nitride 29-Piece
The DW1369 is DEWALT’s most comprehensive TiN-coated set, spanning 29 sizes from 1/16-inch to 1/2-inch in 1/64-inch increments — an unusually fine progression that lets you match fastener hole diameters precisely. The pilot point geometry is a proprietary grind that creates a sharp secondary cutting edge at the tip, which reduces the force needed to start the cut and produces a cleaner entry hole than standard split-point designs.
The tapered web design adds durability toward the shank, where most bits snap under sudden torque spikes. The steel storage case is a standout feature — hinged, wall-mountable, and far more durable than the plastic cases most sets use. It holds each bit in a stamped slot that won’t wear out over repeated opens and closes. The no-spin shank design uses a flat ground into the round shank to bite into the chuck jaws, which works well but is less aggressive than a 3-flat geometry.
Users consistently describe these bits as extremely sharp out of the box, drilling clean holes in both metal and wood with minimal burr formation. The TiN coating extends life significantly compared to uncoated HSS, but for true hardened steel above 50 HRC, the coating alone won’t protect the substrate from annealing at high spindle speeds — these are best paired with slow RPM and steady feed pressure.
What works
- Steel storage case outlasts any plastic alternative on the market
- Pilot point starts cleanly without center punch on thin metal
- 29-piece range includes rare intermediate sizes for precision work
What doesn’t
- TiN coating alone is not ideal for sustained hardened steel drilling
- Bits lack cobalt content — not designed for extreme HRC materials
3. BOYOUYS M35 Four Spiral Flute Step Bit Set
Step bits for hardened steel are rare because conventional single-flute designs overheat at the cutting edge. The BOYOUYS set uses M35 cobalt with four spiral flutes — each flute shares the cutting load, reducing heat concentration and chip welding on the step shoulders. The TiAlN coating on these bits pushes surface hardness past 89 HRC, which is necessary when the step transitions between diameters and the entire edge engages the work simultaneously.
The three-bit set covers 30 total step sizes between 3/16-inch and 1-1/8-inch, with each bit stepping in 1/8-inch increments. The 1/4-inch hex shank is impact-driver compatible, meaning you can run these bits at higher torque without worrying about the shank spinning in a standard chuck. The four-flute design also produces a smoother wall finish than traditional step bits, which is critical when drilling sheet metal for flush-mounted fasteners.
User reports confirm the bits cut fast through mild steel and stainless, though one reviewer noted a loss of sharpness after 7-10 holes through metal studs. For hardened steel specifically, keeping RPM low and using cutting oil will extend edge life significantly — the four-flute design evacuates chips efficiently, but the coating can only do so much if friction exceeds the thermal threshold.
What works
- Four spiral flutes reduce heat buildup compared to standard step bits
- TiAlN coating handles high-temperature cutting environments
- Impact driver hex shank prevents spin-out at high torque
What doesn’t
- Edge sharpness drops after repeated use on hardened steel studs
- Only three bits in the set — limited step range per bit
4. WildBossy M35 Cobalt Drill Bit Set 20pc
The WildBossy M35 set packs 20 fractional-inch bits from 1/16 to 1/2-inch into a compact plastic case at a price point that undercuts most cobalt competitors by a wide margin. The 135-degree split point is ground precisely, and the 3-flat shank provides solid engagement in both keyed and keyless chucks. The titanium surface treatment adds a thin layer of wear resistance, though it is not as durable as a full TiAlN coating.
Customer reports reveal somewhat inconsistent quality control — some users report bits that drill through stainless steel like butter, while others received units where several bits were dull or snapped on first use. This variance suggests the heat treatment or grinding tolerances may not be as consistent as premium brands. Still, the bits that perform well show genuine M35 cobalt hardness, cutting through tapped studs and turbo bolts without annealing.
For the price, this set works as a high-volume shop set where losing or breaking an individual bit is not a disaster. The included size duplicates on smaller diameters (1/16, 5/64, 3/32, 7/64, 1/8, and 3/16 inch each have two pieces) mean you get spares for the most commonly snapped sizes. Not ideal for production work, but for occasional hardened steel drilling it delivers genuine cobalt performance at entry-level cost.
What works
- Genuine M35 cobalt steel at a very accessible price point
- Duplicate smaller bits reduce downtime from snap failures
- 3-flat shank grips chucks firmly without spinning
What doesn’t
- Quality control varies — some bits arrive dull or snap immediately
- Plastic storage case feels flimsy compared to metal alternatives
5. WildBossy M35 Cobalt Metric Drill Bit Set 19pc
This metric companion to the fractional WildBossy set covers 1mm through 10mm in 0.5mm increments — a useful range for European machinery and automotive fasteners where fractional equivalents don’t align. The M35 cobalt substrate is identical to the fractional version, but the coating here is gold oxide rather than titanium. Gold oxide is primarily a cosmetic surface treatment that provides minimal additional hardness compared to TiN or TiAlN, though it does offer some corrosion resistance during storage.
The round straight shank design lacks the 3-flat anti-spin feature found on the fractional set, which can be a disadvantage when drilling hardened steel at high torque — the bit can spin in the chuck if the jaws are not fully tightened. The 135-degree split point is present and performs well, with users reporting clean hole starts in stainless steel and cast iron without walking. The plastic case keeps bits organized, though several users reported the case arrived cracked in shipping.
For metric users who regularly drill hardened alloys, this set provides the right size progression without needing to convert fractional measurements. The cobalt content is genuine and matches the hardness claims, but the round shank and basic coating mean it is better suited for drill press use where chuck grip is stronger, rather than handheld impact drilling where spin-out is a real risk.
What works
- Complete metric range 1-10mm in 0.5mm steps for precision fitting
- M35 cobalt substrate maintains edge hardness in medium-hard metals
- 135-degree split point prevents walking on smooth steel surfaces
What doesn’t
- Round shank lacks anti-spin flats — prone to chuck slippage
- Gold oxide coating adds minimal heat or wear resistance
6. Milwaukee 48-89-4630 TiN Shockwave 15-Piece
Milwaukee’s Shockwave line is designed specifically for impact driver use, and the 48-89-4630 reflects that focus with a 3-flute geometry that increases chip clearance compared to standard 2-flute bits. The TiN coating is applied over a proprietary steel substrate that Milwaukee calls “Shockwave” — a heat-treated alloy that resists the torsional hammering impact drivers deliver. The split point is ground to 135 degrees and provides reliable self-centering on most metals.
At 15 pieces, this set is smaller than most in this guide, covering only the most common sizes from 1/16 to 1/2-inch without duplicates. The bits are jobber length, which is adequate for most metal thicknesses but may struggle to reach through thick stock like a 2×4 — one user noted this specifically. The case is a compact plastic clamshell that stores easily in a tool bag but offers less protection than a full box.
Users consistently praise the durability of these bits, with some claiming they outperform their cobalt bits in impact driver applications. The 3-flute design does evacuate chips faster than standard bits, which helps prevent binding in deep holes. However, for hardened steel specifically, the lack of cobalt in the substrate means these bits will dull faster than M35 alternatives — they are best reserved for impact driver work on mild to medium-hard steel rather than high-HRC alloys.
What works
- 3-flute design clears chips faster than conventional 2-flute bits
- Optimized for impact driver torque characteristics
- Split point starts accurately without center punch
What doesn’t
- No cobalt content limits effectiveness on hardened steel above 50 HRC
- Small bit selection — no duplicates for high-wear sizes
7. HIGHFIRE Hex Shank Drill Bit Set 22pc
The HIGHFIRE set is built around the hex shank concept — each bit has a full-length hex body that locks into quick-change impact driver chucks without any chance of spin-out. The HSS substrate is titanium nitride coated, providing reasonable wear resistance for general metal drilling, though the base material is standard HSS rather than cobalt. The 135-degree split point is accurate and provides good self-centering on flat steel surfaces.
The 22-bit set covers 1/16 through 1/2-inch with doubles on the smallest sizes. The tapered web design adds thickness near the shank to reduce breakage under sudden torque loads — a common failure point in hex shank bits where the transition between the hex body and the flute creates a stress concentration. The double blister pack packaging is basic but functional, though it does not provide organized storage like a case.
User feedback indicates these bits perform well in wood, plastic, and thin metal up to about 1/8-inch thickness. For hardened steel, the HSS substrate and TiN coating will struggle — the bit will cut, but edge life will be short compared to cobalt alternatives. These are best viewed as a high-value general-purpose hex shank set for impact drivers, with the ability to handle occasional hardened steel work when no other option is available.
What works
- Hex shank eliminates spin-out in quick-change impact chucks
- Tapered web design reduces breakage at the shank transition
- Generous size range with duplicates on small bits
What doesn’t
- Standard HSS substrate dulls quickly on hardened steel
- Blister pack offers no organized storage for the bits
Hardware & Specs Guide
M35 Cobalt Steel vs Standard HSS
The defining difference is red hardness — the temperature at which the steel begins to soften and lose its cutting edge. Standard HSS (M2 grade) begins to anneal around 600°F, while M35 cobalt steel maintains its hardness up to approximately 1100°F. This 500°F margin is critical when drilling hardened steel because friction at the cutting edge can easily exceed 800°F. The 5% cobalt content also increases the material’s overall hardness from 62 HRC (M2) to 67 HRC (M35), allowing the bit to scratch through work-hardened surfaces that would dull HSS instantly.
TiAlN Coating Performance
Titanium Aluminum Nitride coating differs from standard TiN in a crucial way: at elevated temperatures, the aluminum in the coating oxidizes and forms a thin layer of aluminum oxide on the surface. This oxide layer has extremely low thermal conductivity, which reflects heat back into the chip rather than letting it conduct into the bit substrate. In practical terms, a TiAlN-coated bit running at 1400°F can have a substrate temperature of only 900°F — keeping the cobalt steel below its annealing threshold even during aggressive cuts. This makes TiAlN the preferred coating for any drill bit intended for sustained hardened steel use.
FAQ
What RPM should I use when drilling hardened steel with a cobalt bit?
Can a standard HSS bit drill through hardened steel with enough cutting oil?
Final Thoughts: The Verdict
For most users, the drill bit for hardened steel winner is the toolant Cobalt Pro 21pc because its TiAlN coating and bullet-point tip deliver genuine hardened-steel performance without the premium pricing of industrial brands. If you need impact driver compatibility with a proven brand name, grab the Milwaukee Shockwave 15pc. And for metric fastener work or step-drilling applications, nothing beats the BOYOUYS M35 Step Bit Set for precision and chip evacuation.