Drilling into steel is a battle of hardness. Standard high-speed steel bits dull fast, overheat, and snap under pressure, turning a quick project into a frustrating fight. The right set of drill bits built specifically for hardened metal changes that equation entirely, letting you cut clean holes without burning through bits every dozen holes.
I’m Mohammad Maruf — the founder and writer behind WellFizz. I’ve spent hundreds of hours analyzing metallurgy, cutting geometries, and real-world performance data across dozens of drill bit sets to separate marketing claims from actual drilling capability.
This guide breaks down the five best sets for drilling into steel. After testing and comparing cobalt content, point angles, and heat resistance, only one set stands as the definitive best drill bits for steel that balances endurance, precision, and value.
How To Choose The Best Drill Bits For Steel
Picking the wrong drill bit for steel means wasted money and ruined workpieces. You need to match the bit’s material grade, point geometry, and coating to the specific steel hardness you’re drilling. Here are the three factors that separate a set that lasts from one that disappoints.
Cobalt Content Determines Heat Tolerance
Standard HSS bits soften above 600°F, which happens fast when drilling steel. Cobalt-added HSS (M35 with 5% cobalt or M42 with 8% cobalt) retains hardness up to 1100°F. For hardened steel, stainless, or cast iron, stick with at least 5% cobalt. Lower-cost bits labeled “cobalt” sometimes contain surface treatment only — real cobalt is uniform throughout the steel matrix.
135° Split Point vs 118° Conventional Point
A 118° point works fine for wood and soft metals but wanders on steel. A 135° split-point geometry creates a self-centering chisel edge that bites immediately without a center punch. This reduces walking, eliminates pilot hole need on many jobs, and cuts through scale or rounded surfaces cleaner. Every bit in this guide uses the 135° split-point design.
Flute Design and Shank Type Matter for Chip Clearance
Deep holes in steel generate long, hot chips that clog standard flutes. Look for fully ground spiral flutes with a polished finish — these eject chips faster and lower friction. A straight round shank fits standard 3/8-inch and 1/2-inch chucks, but ensure the shank isn’t undersized or it will spin under heavy torque. Flat-ground shank relief prevents chuck slippage on high-torque applications.
Quick Comparison
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| Model | Category | Best For | Key Spec | Amazon |
|---|---|---|---|---|
| STROTON Cobalt 17-Piece | Cobalt HSS | High-volume steel drilling | 5% Cobalt, 68 HRC hardness | Amazon |
| Milwaukee Shockwave 15-Piece | TiN Coated HSS | General steel + impact driver use | 1/4″ hex shank, TiN coating | Amazon |
| RCINDUS Cobalt 15-Piece | Cobalt HSS | Budget-friendly hardened steel | M35 cobalt, 135° split point | Amazon |
| ZNXIMER Cobalt 16-Piece | Cobalt HSS | Mixed-material projects | 5% Cobalt, fully ground flutes | Amazon |
| PLATINUMEDGE Step Bit Set | Step Drill HSS | Thin sheet metal deburring | 5 bits, 50 step sizes | Amazon |
In‑Depth Reviews
1. STROTON Cobalt 17-Piece Set
The STROTON set delivers genuine 5% cobalt M35 steel with a 68 HRC hardness rating — that’s tough enough to chew through stainless, hardened steel, and cast iron without losing edge quickly. Each bit has a triple-ground cutting edge and a 135° split point that self-centers immediately on curved steel surfaces. The range spans 1/16-inch up to 1/2-inch, with duplicates of the most-worn sizes (1/16, 3/32, 1/8, and 1/4 inch) so you don’t have to stop mid-project.
Real-world tests show this set drilling eight half-inch holes through quarter-inch steel plate with one bit and staying sharp after 24+ mixed holes. The storage case uses tight bit clamps and a positive-lock latch — bits don’t rattle loose. For heavy-volume steel drilling in a shop environment, this is the set that holds up longest per dollar.
The only drawback is brittleness in the smallest bits (under 3/16-inch) under aggressive feed pressure on thin metal studs. Keep speeds moderate and use cutting oil to reduce heat buildup. The manufacturer backs it with a free replacement warranty, which several users have successfully redeemed.
Why it’s great
- Genuine M35 cobalt with verified 68 HRC hardness
- Triple-ground 135° split point for instant bite
- Includes duplicate size bits for common diameters
- Free replacement warranty honored by manufacturer
Good to know
- Smallest bits (under 3/16″) can snap under high pressure
- Case clamps are tight but hard to open with thick gloves
2. Milwaukee Shockwave 15-Piece TiN Set
The Milwaukee Shockwave set uses titanium nitride (TiN) coating over high-speed steel to reduce friction during drilling. This coating lowers heat generation, which extends bit life in steel compared to uncoated HSS. The 1/4-inch hex shank makes these compatible with impact drivers and quick-change chucks, so you can swap between drilling and driving without rechucking.
What sets the Shockwave apart is its optimized flute geometry for chip ejection in steel. The flute profile is designed to pull chips upward instead of packing them into the hole. For electricians, metal fabricators, and anyone drilling into steel studs or thin plate repeatedly, the hex shank saves significant time on fastening-heavy jobs.
The TiN coating reduces friction but does not increase the bit’s core hardness — these bits will dull faster on hardened steel than a straight cobalt bit. Stick to mild steel, aluminum, and sheet metal for best performance. The kit includes 15 bits covering 1/8-inch to 1/2-inch diameters.
Why it’s great
- 1/4″ hex shank fits impact drivers directly
- TiN coating reduces friction and heat buildup
- Optimized flute geometry clears steel chips efficiently
Good to know
- Not rated for hardened or stainless steel drilling
- Bits lack split-point design for self-centering
3. RCINDUS Cobalt 15-Piece Set
The RCINDUS set proves you don’t need to spend premium money for real M35 cobalt bits. Each piece is fully ground and hardened through a dozen manufacturing processes, with diameter control held within -0.03mm for consistent fit. The 135° split point centers reliably on stainless and cast iron without a pilot hole, reducing walking on smooth steel surfaces.
User reports confirm these bits drill through 1/8-inch steel plate for ten successive holes with no measurable dulling. One review highlighted using a single bit to extract 25 stripped screws before it required sharpening — a testament to the M35 material’s heat tolerance. The 15-piece set is all 1/4-inch diameter, which is a limitation if you need multiple sizes, but ideal if you work primarily with one hole diameter on steel.
The plastic storage case is functional but basic — bits can shift during transport if the case is tossed in a toolbox. For consistent steel drilling on a tight budget, these bits deliver performance that rivals sets costing significantly more.
Why it’s great
- Real M35 cobalt with tight diameter tolerance
- 135° split point prevents walking on steel
- Exceptional heat resistance for long bit life
Good to know
- All bits are 1/4″ diameter — no size variety
- Storage case is basic with loose bit retention
4. ZNXIMER Cobalt 16-Piece Set
ZNXIMER’s set offers 5% cobalt M35 steel with a fully ground spiral flute design that clears chips aggressively during steel drilling. The 135° split point is present on every bit, and the straight shank includes a flat-ground relief that prevents chuck slippage under high torque. The set spans 1/16-inch to 3/8-inch with duplicates of the four most common sizes — a thoughtful layout for mixed-material shops.
Test results show these bits drilling 24+ holes through wood and a steel trailer frame using only two bits, with the flat shank grip holding firm in a standard drill chuck. The indexing storage case keeps every bit organized with labeled slots, making size selection fast. For users who switch between steel, aluminum, wood, and plastic, the wide application range is a clear advantage.
One caveat: spark testing suggests the cobalt content may be lower than 5% in some batches, with a mix of HSS and cobalt spark patterns visible. This doesn’t affect performance on mild steel or cast iron but could reduce lifespan on very hard alloys above HRC38. Still, for the price point, the build quality and sharpness out of the box are impressive.
Why it’s great
- Fully ground spiral flutes for fast chip ejection
- Flat-ground shank eliminates chuck slippage
- Indexed case with size duplicates for common diameters
Good to know
- Cobalt content may be lower than 5% in some batches
- Not designed for hardened steel above HRC38
5. PLATINUMEDGE Step Drill Bits Set
The PLATINUMEDGE set is not a traditional twist drill — it’s five step bits made from 4241 HSS with nitride black coating and polished flutes. Each bit creates multiple hole sizes through sheet metal by simply advancing the step to the right diameter. The set covers 50 total step sizes ranging from 1/8-inch to 1-3/8-inch, which replaces dozens of individual bits for electricians and HVAC workers drilling steel enclosures.
The double-flute design cuts faster than single-flute step bits and ejects particles cleanly, preventing chip buildup inside the hole. The nitride coating adds surface hardness and reduces galling on soft steel and aluminum. Users report using these daily for five days a week in fabrication work with no loss of sharpness — a strong durability signal for an entry-level step bit set.
Step bits excel on thin sheet metal but struggle on thick steel plate (over 1/4-inch) where a twist drill is more efficient. The largest bit (1-3/8-inch) requires a drill with decent torque, and the storage box is compact but not impact-resistant. For anyone regularly making clean, burr-free holes in steel sheet, this is the most versatile option.
Why it’s great
- 5 bits replace dozens of individual sizes for sheet metal
- Double-flute design for faster, smoother cutting
- Nitride coating reduces heat and galling on steel
Good to know
- Not effective on steel plate thicker than 1/4″
- Storage box is lightweight and not shop-rugged
FAQ
Can I use standard HSS bits on hardened steel?
What is the best RPM for drilling steel with cobalt bits?
Why do my drill bits keep breaking when drilling steel?
Final Thoughts: The Verdict
For most users, the best drill bits for steel winner is the STROTON Cobalt 17-Piece Set because its 5% M35 cobalt, 68 HRC hardness, and triple-ground split point deliver consistent, long-lasting performance across mild steel, stainless, and cast iron. If you need quick bit swaps with an impact driver, grab the Milwaukee Shockwave TiN Set. And for clean, burr-free holes in sheet metal, nothing beats the versatility of the PLATINUMEDGE Step Bit 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.