Drilling into hardened steel is one of the most punishing tasks you can throw at a drill bit. Standard high-speed steel bits dull instantly, generate dangerous heat, and often skid across the surface before ever biting in. The difference between a successful pilot hole and a ruined workpiece comes down to the metallurgy and geometry of the bit in your chuck.
I’m Mohammad Maruf — the founder and writer behind Gardening Beyond. I’ve spent years studying the material science of cutting tools, comparing cobalt alloys and heat-treating processes, and analyzing aggregated owner feedback to separate the bits that truly cut from the ones that just look the part.
This guide breaks down the real-world performance of the seven most serious contenders on the market so you can confidently choose the right bits for drilling hardened steel for your next job without wasting money on hype.
How To Choose The Best Bits For Drilling Hardened Steel
When you’re pushing a bit into a material that measures 60+ on the Rockwell C scale, three factors separate a clean hole from a smoking mess: the base alloy, the point geometry, and the surface coating. Ignore any of these, and you’ll be buying a replacement set before lunch.
Cobalt Content and Hardness Rating
Look for bits labeled M35 or higher — that means the steel alloy contains at least 5% cobalt. This addition allows the bit to retain its cutting edge at the high temperatures generated when drilling hardened steel. A hardness rating of 67 HRC or higher is the threshold you want. Bits below this will lose temper quickly and become useless on the second or third hole.
Point Geometry: Split Point vs. Pilot Point vs. Bullet Point
A 135-degree split point is the industry standard for hardened materials. The split creates a self-centering action that stops the bit from walking across the surface. Some premium sets use a pilot-point or bullet-point tip that achieves the same goal with a slightly different grind. Avoid conventional 118-degree points — they skate on hardened steel and require a center punch for every single hole.
Coating Technology for Heat Management
Uncoated cobalt bits work well if you use cutting oil and slow speeds, but a good coating extends bit life significantly. Titanium Nitride (TiN) reduces friction and adds surface hardness. Titanium Aluminum Nitride (TiAlN) is even better — it actually becomes harder as the cutting temperature rises, making it ideal for sustained drilling in stainless and hardened alloys.
Quick Comparison
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| Model | Category | Best For | Key Spec | Amazon |
|---|---|---|---|---|
| toolant Cobalt Pro 21pc | Premium Coated | Heavy-duty metal drilling | TiAlN coating, 89 HRC | Amazon |
| DEWALT DW1369 29pc | Premium TiN | Versatile workshop set | Pilot point, TiN coated | Amazon |
| Narwhal 3/4 in 3-Pack | Large Diameter | Big holes in thick steel | 3/4 in diameter, M35 cobalt | Amazon |
| STROTON Cobalt 17pc | Mid-Range Cobalt | General hardened metal drilling | M35 steel, 68 HRC | Amazon |
| WildBossy M35 20pc | Value Cobalt Set | Budget entry into cobalt | Ti surface, 3-flat shank | Amazon |
| Milwaukee 48-89-4630 15pc | Mid-Range TiN | Light-to-medium steel tasks | TiN coating, 3-flute | Amazon |
| Mudder M35 100-Pack | Bulk Cobalt | High-volume 1/8 in drilling | 100 pcs, single size | Amazon |
In‑Depth Reviews
1. toolant Cobalt Drill Bit Set Pro, 21pc
The toolant Pro set brings the most advanced coating technology in this lineup — Titanium Aluminum Nitride — which pushes surface hardness to 89 HRC and stays aggressive as heat rises. The 21-piece range covers 1/16-inch through 1/2-inch, with duplicates on the most common small sizes. The bullet-point tip geometry is specifically designed for self-centering on hardened surfaces, eliminating the need to center-punch every hole.
Users report drilling through heavy-duty trailer frames and thick stainless plates without noticeable dulling after dozens of holes. The 3-flat shank prevents spinning in the chuck even under high torque, a genuine advantage when the bit bites deep. The 90-day warranty and responsive customer service add confidence for a set at this tier.
The only downside is that the TiAlN coating makes the bits more brittle under extreme lateral stress — drilling into hard resin or glass-like materials can snap the smaller diameters. Stick to metal and steel, and this set outperforms everything else here.
What works
- TiAlN coating outlasts standard TiN on hardened alloys
- Bullet-point tip prevents walking on smooth steel surfaces
- Excellent size range with duplicates on popular small diameters
What doesn’t
- Small bits can snap under side load in non-metal materials
- Premium price point compared to uncoated cobalt sets
2. DEWALT Titanium Nitride Coated Drill Bit Set, 29-Piece (DW1369)
The DW1369 is the most complete set in this roundup with 29 pieces spanning from 1/16-inch to 1/2-inch in precise 1/64-inch increments. The pilot-point geometry starts cutting on contact, which is a major time-saver on thin sheet metal and hardened steel alike. The titanium nitride coating extends edge life noticeably compared to uncoated HSS, though it does not match the high-heat performance of TiAlN on sustained cuts.
The metal storage box is a standout — it feels far more durable than the plastic cases that come with most competitors, and it can be wall-mounted. Long-term owners report these bits survive repeated use on mild steel and cast iron with only occasional sharpening. The tapered web design reduces breakage on the smaller shanks, a weak point in many budget sets.
On hardened steel specifically, the pilot point helps with starting accuracy, but the TiN coating will eventually struggle if you push feed rates too hard without cutting oil. This set is best for a workshop that needs one versatile box for mixed materials rather than a dedicated hardened-steel specialist.
What works
- 29-piece set covers nearly every fractional size needed
- Pilot point starts instantly without walking
- Rugged metal case outlasts plastic alternatives
What doesn’t
- TiN coating not as heat-resistant as TiAlN on heavy cuts
- Plastic bit holder within case has sizes that wear off over time
3. Narwhal 3/4 in Cobalt Drill Bits, 3-Pack
Most hardened steel bit sets stop at 1/2-inch, leaving anyone needing larger holes scrambling for specialty tooling. Narwhal solves that with a 3-pack of 3/4-inch M35 cobalt bits featuring a 135-degree split point and full-ground flutes. Each bit has a 3-inch flute length and 6-inch total length, enough to penetrate thick plate and structural steel without binding.
Customer reports show these bits drilling 70+ holes in thin stainless and holding their edge through aluminum timing covers during supercharger installations. The fully ground construction ensures the diameter stays true, which matters when you need a precise fit for a bolt or pin. The included plastic case is tough enough for job-site travel.
These are not the bits for everyday small repairs — they are specialized tools for big jobs. You will need a drill or drill press with enough torque to spin a 3/4-inch bit at the correct slow speed, and cutting fluid is strongly recommended for every hole.
What works
- 3/4-inch diameter fills a gap most sets ignore entirely
- M35 cobalt holds up to sustained high-temperature drilling
- True-to-size diameter for precision fit applications
What doesn’t
- Only three bits for a specialized large-diameter use case
- Requires powerful drill and proper slow-speed technique
4. STROTON Cobalt Drill Bit Set, 17pc
STROTON’s 17-piece set is the crowd favorite for a reason — it delivers genuine M35 cobalt at a mid-range price point with hardness rated at 68 HRC. The three-times ground cutting edge produces long, clean chips rather than grinding dust, a sign that the bit is actually shearing material rather than rubbing it off. Users report drilling eight half-inch holes through quarter-inch steel with the same bit still cutting aggressively.
The 135-degree split point centers reliably, and the included plastic case holds each bit securely with tight clamps that prevent rattling and dulling during storage. The company backs the set with a warranty that replaces broken bits, which is rare at this price. Several long-term users mention the set has outperformed more expensive brands they’ve owned for decades.
A minority of users report brittleness in the sub-3/16-inch bits, particularly on thin metal studs where lateral pressure is easy to apply. Using the correct speed and a steady feed rate solves most of those failures, but the smaller sizes are definitely the weak link here.
What works
- Genuine M35 cobalt with 68 HRC for real hardened steel work
- Triple-ground edge creates clean chip-cutting action
- Warranty covers broken bits, a rare guarantee at this tier
What doesn’t
- Smallest bits under 3/16-inch can snap under lateral load
- Plastic case clamps are tight but not job-site tough
5. WildBossy M35 Cobalt Drill Bit Set, 20pc
WildBossy offers the most affordable entry into M35 cobalt with a 20-piece set that includes duplicate small sizes and a plastic index case. The bits feature a titanium surface treatment and a 3-flat shank that prevents spinning in the chuck — a feature usually reserved for more expensive sets. The 135-degree split point is present and effectively reduces walking on initial contact.
Real-world feedback shows these bits drilling through snapped taps and studs in turbocharger applications, which is about as demanding as it gets for a budget cobalt set. Users note that thin stainless steel is handled easily with slow cutting speeds. The set is not recommended for glass or ceramic, and the manufacturer explicitly advises speed and heat control.
Quality control is the trade-off at this price point. Some users report receiving sets where a few bits were dull out of the box or snapped on the first attempt. The majority of bits in each set perform well, but inconsistency means you may need to test each size before committing to a critical job.
What works
- Lowest cost entry point for M35 cobalt bits
- 3-flat shank prevents chuck spinning under load
- 20-piece set with duplicates on common small sizes
What doesn’t
- Inconsistent quality — some bits arrive dull or snap easily
- Not suitable for glass, ceramic, or brittle materials
6. Milwaukee 48-89-4630 TiN Shockwave, 15-Piece
Milwaukee’s Shockwave set is a 15-piece titanium nitride coated kit with a 3-flute design that differentiates it from the standard 2-flute bits in this comparison. The third flute helps clear chips faster during high-speed drilling, which reduces heat buildup in the cutting zone. The 135-degree split point is present, and the TiN coating provides a slick surface that resists welding on softer metals.
This set is best suited for a mixed-use workshop where you drill into wood, plastic, and light steel regularly. The bits start cleanly and the case is well-organized. Users consistently rate the set as a solid performer for general-purpose drilling, with the durability you expect from the Milwaukee brand.
On hardened steel specifically, the TiN coating will not match the thermal resilience of cobalt alloys or TiAlN coatings. The smaller bits are relatively short, which can be an issue when drilling through thicker material like a 2×4 board. This is a good secondary set for quick jobs, not the primary choice for sustained hardened steel work.
What works
- 3-flute design clears chips faster than standard 2-flute bits
- TiN coating reduces friction on mixed materials
- Reputable Milwaukee build quality and case design
What doesn’t
- TiN coating lacks high-heat endurance for sustained hardened steel drilling
- Smaller bits are too short for thicker stock
7. Mudder M35 Cobalt Drill Bit Set, 100-Piece (1/8 Inch)
If your work revolves around drilling 1/8-inch holes in hardened steel by the hundreds, the Mudder 100-pack is the most economical route available. All bits are made from M35 cobalt high-speed steel with a 135-degree split point and a hardened honed cutting edge. The bits are uncoated, which means performance relies entirely on the base alloy and your cutting technique.
Users report that these bits stay sharp through multi-layer metal roofing applications and handle high torque without becoming brittle. The price per bit is drastically lower than any multi-size set, making this a no-brainer for production environments or shops that need to drill pilot holes at scale. The bits are shorter than standard jobber length, which helps with rigidity but limits reach.
The single-size limitation is the obvious trade-off — you get only 1/8-inch bits. If your project requires a range of diameters, you will need to buy additional sets. The uncoated surface also means you must use cutting oil more liberally than with coated bits to prevent heat buildup.
What works
- 100 bits for a fraction of the per-bit cost of multi-size sets
- M35 cobalt alloy handles hardened metal with proper technique
- Shorter length adds rigidity for precise 1/8-inch holes
What doesn’t
- Only 1/8-inch diameter — no size variety included
- Uncoated bits require more cutting oil to manage heat
Hardware & Specs Guide
M35 Cobalt Steel (5% Cobalt)
M35 high-speed steel incorporates 5% cobalt into the alloy, which allows the bit to retain its hardness at elevated cutting temperatures. Bits made from M35 typically measure 67-68 HRC on the Rockwell hardness scale. This is the minimum standard for reliable drilling into hardened steel, stainless steel, and cast iron. Lower-cobalt or HSS-only bits will soften and dull rapidly under the same conditions.
135-Degree Split Point
The 135-degree angle is steeper than the traditional 118-degree point, which makes the bit self-centering and reduces the need for a center punch. The split point creates a chisel edge that actively cuts rather than pushing material aside, resulting in cleaner holes and less walking on curved or uneven surfaces. This geometry is essential for precision work on hardened steel.
TiAlN vs. TiN Coatings
Titanium Aluminum Nitride (TiAlN) outperforms standard Titanium Nitride (TiN) in high-temperature applications because the aluminum component oxidizes at the cutting edge, forming a hard ceramic layer that actually increases surface hardness as heat rises. TiAlN can reach 89 HRC surface hardness. TiN retains around 80 HRC and is better suited for general-purpose drilling where sustained high heat is not the primary concern.
3-Flat Shank vs. Round Shank
A 3-flat shank has three ground flats that provide additional grip points in the drill chuck, preventing the bit from spinning under high torque. This is especially important when drilling hardened steel because the cutting forces are significantly higher than with wood or soft metals. Round shanks can slip even when fully tightened, leading to bit damage and inaccurate holes.
FAQ
Can standard HSS bits drill through hardened steel?
What speed should I use when drilling hardened steel with cobalt bits?
Do I need cutting oil for cobalt drill bits on hardened steel?
How do I know if my drill bit is actual M35 cobalt and not just painted HSS?
Final Thoughts: The Verdict
For most people needing a reliable set for regular hardened steel work, the winner is the toolant Cobalt Drill Bit Set Pro because its TiAlN coating and bullet-point tip deliver consistent performance across the widest range of demanding materials. If you want a complete workshop set that handles everything from wood to steel, grab the DEWALT DW1369. And for production-scale 1/8-inch drilling or large-diameter holes, nothing beats the value of the Mudder 100-Pack or the capability of the Narwhal 3-Pack.