Drilling into hardened steel with a standard high-speed steel bit is a recipe for smoking metal, destroyed tips, and a stalled project. The material demands a bit that can withstand extreme heat and abrasive wear without losing its edge. Cobalt-infused high-speed steel and specialized geometries are the only real answers here—anything less is simply not up to the task.
I’m Mohammad Maruf — the founder and writer behind WellFizz. My buying guides are built on deep market research and rigorous specification analysis, comparing dozens of products to isolate the exact materials, coatings, and point geometries that deliver real performance in demanding metal-drilling applications.
Whether you are a professional fabricator or a dedicated DIYer, choosing the right tool can mean the difference between a clean hole and a ruined workpiece. This guide breaks down the best options available so you can find the perfect set of drill bits for hardened steel that match your shop’s needs and your budget.
How To Choose The Best Drill Bits For Hardened Steel
Selecting the right bit for hardened steel involves more than just grabbing the most expensive set. You need to assess the material composition, the geometry of the cutting tip, and the practicality of the kit’s size range. The wrong choice leads to premature dulling, overheating, and potential damage to your workpiece or drill.
Material: Cobalt Content is King
Standard high-speed steel (HSS) simply cannot handle the hardness of alloys like stainless steel or tool steel. M35 cobalt steel, containing 5% cobalt, raises the bit’s red hardness, allowing it to maintain its cutting edge even at the elevated temperatures generated when drilling tough materials. Look for sets explicitly labeled as M35 or M42 cobalt for any serious hardened steel work.
Point Geometry: The 135° Split Point Advantage
A 135° split point is the standard for metal drilling because it is blunter than a standard 118° point, which means the cutting edge contacts the surface more abruptly, requiring less force to penetrate. The split point also self-centers, preventing the bit from “walking” across the surface, which is critical for accuracy when you are about to drill a precision hole in expensive material.
Set Composition and Storage
Consider whether the kit covers the sizes you actually need. Fractional sets (1/16″ to 1/2″ by 64ths) are the industry standard for North American work, while metric sets suit international projects or specific machinery. An organized, durable case—preferably metal or hard plastic with clearly labeled slots—keeps the bits protected and accessible, saving frustration on a busy job site or in a crowded workshop.
Quick Comparison
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| Model | Category | Best For | Key Spec | Amazon |
|---|---|---|---|---|
| Norseman 44170 Ultra Dex | Premium HSS | Precision machining and aerospace-standard work | M2/M7 HSS, 135° split point, NAS 907B | Amazon |
| toolant 108Pcs Cobalt Set | Premium Cobalt | Heavy-duty shop use with size redundancy | M35 cobalt, 108-piece kit | Amazon |
| Sinyeenglon 99Pcs Cobalt Set | Mid-Range Cobalt | High-volume jobs with spare small bits | M35 cobalt, 99-piece kit | Amazon |
| Yougfin 29Pcs M35 Cobalt Set | Mid-Range Cobalt | General fabrication and construction drilling | M35 cobalt, 135° split point | Amazon |
| CaRoller 29Pcs Cobalt Set | Mid-Range Cobalt | Portable on-site drilling with cup case | M35 cobalt, amber coating | Amazon |
| MACXCOIP Metric 25Pcs Cobalt Set | Mid-Range Cobalt | Metric-only work and 3D print post-processing | M35 cobalt, 1.0mm–13.0mm range | Amazon |
| HIDOTOL 115Pcs Cobalt Set | Premium Cobalt | Complete workshop coverage with letter/ wire sizes | M35 cobalt, includes fractional, letter, wire | Amazon |
In‑Depth Reviews
1. Norseman Drill Bits 44170 Ultra Dex 29 Piece Set
This Norseman set is a favorite among machinists and tradespeople who demand repeatable, precise holes in tough alloys. The Ultra Dex line meets the NAS 907B aerospace standard, indicating a level of quality control and dimensional accuracy that consumer-grade sets simply do not match. The 135° split point is precision-ground on every bit from 1/16″ to 1/2″ by 64ths, ensuring near-zero walking on startup.
The material is a special Hi-Molybdenum tool steel (M2/M7), not standard cobalt, but the gold oxide coating helps retain cutting fluid and reduces friction. Real-world reports show a single bit drilling over 100 half-inch holes in quarter-inch steel plate and still holding an edge. The set’s consistency means less time swapping bits and more confidence on critical cuts.
The included plastic case is functional but not as rugged as some metal boxes. For the premium price, you are paying for industrial-grade precision rather than a high count of duplicate bits. This is the set for the user who needs a guaranteed outcome on every hole.
Why it’s great
- Aerospace-standard accuracy with a precise 135° split point.
- Exceptional wear life—one bit can last through more than 100 holes in steel plate.
- Gold oxide finish helps retain cutting oil for cooler drilling.
Good to know
- Not cobalt steel; relies on Hi-Molybdenum tool steel formulation.
- Plastic case is adequate but not impact-resistant.
- Premium price for a 29-piece set.
2. toolant 108Pcs Cobalt Drill Bit Set
The toolant set provides an enormous quantity of 108 bits—including multiple duplicates of the most commonly used small sizes—making it an ideal choice for a shop that loses or breaks bits with regularity. The bits are made from M35 cobalt steel and feature a 135° self-centering split point, delivering clean starts and efficient chip evacuation through the spiral flutes.
Real-world testing confirms these bits handle heavy I-beam steel and even tempered steel with relative ease, especially when used with cutting oil and a slow drill speed. The inclusion of fifteen 1/16″ bits and fifteen 5/64″ bits means you won’t be left stranded after snapping a small bit on a tight hole.
Each bit comes sealed in an individual plastic bag inside a compact, hard-plastic case. While the case markings can be difficult to read in low light, the organization and protection are solid. For a mid-range price, this set balances quantity and quality effectively for dedicated DIYers and professionals.
Why it’s great
- Massive 108-piece count with duplicate small sizes.
- M35 cobalt material with heat treatment for extended life.
- Individual sealed bags keep bits moisture-free.
Good to know
- Case markings are small and hard to read.
- Bits can shift in the case during transport.
- Not ideal for precision aerospace work.
3. Sinyeenglon 99Pcs Cobalt Drill Bit Set
This Sinyeenglon set focuses on providing generous spares of the most frequently used small-diameter bits, with sixteen 1/16″ bits and fifteen 5/64″ bits in the kit. The core material is M35 cobalt high-speed steel, ground using a fully hardened process that increases wear resistance and sharpness retention compared to standard titanium-coated bits.
The 135° split point is present on all bits, and the twist flute design effectively lifts chips out of deep holes. Users consistently report that these bits cut through 3/16″ steel beams and thick blocks without overheating, provided you keep the speed low and use cutting fluid. The set includes sizes up to 3/8″ in the fractional range.
The plastic storage case is hard and features a lid with printed size charts for each compartment. However, the adhesive size labels that come with the bits tend to fall off quickly. The case itself is well-organized and secure. This is a strong mid-range option for anyone drilling a high volume of holes on a budget.
Why it’s great
- Excellent quantity of small bits for high-volume work.
- M35 cobalt with hardened full grinding for durability.
- Drills steel effectively at low speed without overheating.
Good to know
- Included size stickers fall off quickly.
- Largest bit is only 3/8″.
- Plastic case is adequate but not heavy-duty.
4. Yougfin 29Pcs M35 Cobalt Drill Bit Set
The Yougfin set is a classic jobber-length fractional kit covering 1/16″ to 1/2″ in 64th-inch increments. Made from M35 cobalt steel, these bits offer a good balance of red hardness and wear resistance for everyday hardened steel tasks. The 135° split point and twisted flute design are optimized for metal chip evacuation.
Customer feedback highlights that these bits stay sharp through repeated use on stainless steel and alloy steel, provided you work with cutting oil and moderate feed pressure. The set includes 29 pieces, all stored in a clear plastic index case with labeled slots. Some users noted that the case hinges can wear over time, but the bits themselves maintain a sharp edge.
This set is a straightforward, no-frills option that gets the job done. It is a strong choice for the home DIYer or light fabrication work where you need a reliable range of cobalt bits without paying for extras you will not use.
Why it’s great
- Complete fractional coverage from 1/16″ to 1/2″.
- M35 cobalt provides good heat resistance.
- Sharp out of the box with clean cutting action.
Good to know
- Plastic case can break at the hinge over time.
- No duplicate small bits if you snap one.
- Requires cutting oil for best performance on stainless.
5. CaRoller Cobalt Drill Bit Set 29-Piece
The CaRoller set distinguishes itself with a unique cup-type round carrying case that clips onto a tool belt, ideal for electricians, plumbers, and steel erectors who need bits within arm’s reach at height. The bits are made from HSS cobalt steel with an amber coating intended to reduce friction and improve wear resistance.
The 135° split point design self-centers effectively, and users have reported drilling 30 holes in a steel I-beam with a single bit before noticing significant edge wear—a testament to its toughness when used at slow spindle speeds with appropriate pressure. The set covers the full 1/16″ to 1/2″ fractional range.
The flexible plastic cup case is convenient but may not protect bits as well as a clamshell case in a packed toolbox. The amber coating on the bits can wear off with heavy use, but base cobalt material still provides good heat resistance. This is a smart choice for anyone prioritizing on-site portability and quick access.
Why it’s great
- Tool-belt clip case for immediate on-site access.
- Excellent performance in I-beam steel.
- Amber coating reduces friction and heat build-up.
Good to know
- Cup case offers less bit protection than a hard case.
- Coating can wear off with heavy use.
- Not the largest size range in this list.
6. MACXCOIP Metric 25Pcs M35 Cobalt Drill Bit Set
For those working with metric hardware, imported machinery, or post-processing metric-sized 3D prints, this MACXCOIP set fills a specific niche. It provides 25 M35 cobalt bits from 1.0mm up to 13.0mm in 0.5mm increments, covering the vast majority of metric drilling requirements. The 135° spear point design aids self-centering on contact.
Users, including a former CNC machinist, report that the bits are sharp and effective on both soft and hard metals. The compact metal storage case is flat enough to slide into shallow tool chest drawers, saving valuable workshop space. Each bit slot is clearly labeled for quick identification.
One minor concern involves the shank strength: a user reported a shank slipping in a drill press chuck under load, potentially due to the material finish. The set also explicitly states it is not applicable for drilling into quenched bolts. For metric-specific work, however, this kit offers precision and convenience.
Why it’s great
- Complete metric progression from 1mm to 13mm.
- Compact metal case fits in shallow drawers.
- Sharp bits with good self-centering action.
Good to know
- Not suitable for hardened bolts or quenched steel.
- Shank surface can slip in some chucks.
- Limited to 25 pieces — no duplicate small bits.
7. HIDOTOL 115PCS Cobalt Drill Bit Set
This HIDOTOL set is the most comprehensive kit in the lineup, combining fractional (1/16″–1/2″ by 64ths), letter sizes (A–Z), and wire gauge sizes (#1–#60) into a single metal case. It is the ultimate solution for a workshop that needs to match pre-existing tapped holes or follow engineering drawings without resorting to multiple separate sets.
The M35 cobalt material and 135° split point are present across all bits, and the fully ground twist design helps clear particles quickly. Users note that even the smallest wire gauge bits are correctly ground with a double bevel, which is uncommon at this price point. The bits drill through hard materials that would stall typical HSS bits.
The metal index case is sturdy and keeps everything organized with clear markings. At over seven pounds, this set is not designed for portable belt carry—it is intended for bench or tool chest storage. If you need total drilling flexibility and want every standard size at hand, this kit is the one.
Why it’s great
- Covers fractional, letter, and wire gauge sizes completely.
- Sturdy metal case for long-term storage.
- Even small bits are ground with precision.
Good to know
- Heavy kit (over 7 lbs) — not portable.
- Some sizes are single pieces only.
- Premium price reflects the comprehensive range.
FAQ
Can I use cobalt drill bits on hardened steel without cutting oil?
What is the ideal RPM for drilling hardened steel with these bits?
Are letter and wire gauge drill bits necessary for hardened steel work?
Final Thoughts: The Verdict
For most users, the drill bits for hardened steel winner is the toolant 108Pcs Cobalt Set because it provides professional M35 cobalt performance with enough spare bits to keep working through long jobs. If you want aerospace-grade precision and a legendary reputation for longevity, grab the Norseman 44170 Ultra Dex Set. And for complete workshop coverage with fractional, letter, and wire sizes in one metal case, nothing beats the HIDOTOL 115Pcs Cobalt Set.
Mo Maruf
I created WellFizz to bridge the gap between vague wellness advice and actionable solutions. My mission is simple: to decode the research and give you practical tools you can actually use.
Beyond the data, I am a passionate traveler. I believe that stepping away from the screen to explore new environments is essential for mental clarity and physical vitality.