Drilling into steel demands a bit that can withstand extreme heat and abrasion without dulling after a few holes. The wrong bit wanders on contact, rounds off, or snaps under torque, turning a five-minute job into a frustrating hour of rework and wasted material.
I’m Mo Maruf — the founder and writer behind The Tools Trunk. I’ve spent years analyzing metallurgy, coating technologies, and geometry specs across hundreds of drill bit sets to understand what actually separates a frustrating experience from clean, repeatable cuts in ferrous metals.
This guide breaks down the specific material grades, point geometries, and coatings that determine real-world performance, helping you confidently choose the drill bit for steel that matches your specific drilling demands and budget tier.
How To Choose The Best Drill Bit For Steel
Selecting a bit for steel work involves understanding three key elements: the base material of the bit, its tip geometry, and the coating applied to it. Each factor directly impacts how the bit starts, cuts, and survives the heat generated by friction against hard metal. Ignoring any one of these leads to premature dulling or breakage.
Material Grade: HSS vs Cobalt
Standard high-speed steel (HSS) works for mild steel and occasional use, but it softens quickly when the workpiece exceeds 600°F. Cobalt steel, specifically M35 (5% cobalt) and M42 (8% cobalt), retains its hardness at much higher temperatures, allowing faster feed rates and longer edge life on stainless steel, hardened alloys, and thick plate. M42 is the premium tier, offering the highest red hardness for industrial-style drilling on tough materials like Inconel or titanium.
Point Geometry: The 135° Split Point Standard
Steel surfaces are slick. A standard 118° point tends to skate or walk before engaging. A 135° split point creates a secondary cutting edge that bites immediately on contact, reducing the need for center-punching and producing rounder holes from the first revolution. This geometry is non-negotiable on hardened steel and essential for any serious metal drilling.
Coating and Flute Design
Black oxide provides corrosion resistance and helps retain lubricant but adds minimal heat protection. Titanium aluminium nitride (TiAlN or AlTiN) coatings offer much higher oxidation resistance and surface hardness, ideal for dry drilling or high-RPM work. The flute design must also eject chips efficiently — parabolic flutes clear material faster from deep holes, reducing the risk of binding or overheating in heavy sections of steel.
Quick Comparison
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| Model | Category | Best For | Key Spec | Amazon |
|---|---|---|---|---|
| Drill America D/A29J-CO-PC | Premium Cobalt Set | Heavy industrial & hardened steel | M42 Cobalt / 135° split point | Amazon |
| toolant 108Pcs Cobalt Set | Large M35 Kit | Jobsite versatility & bulk drilling | M35 Cobalt / 108 bits | Amazon |
| EZARC Step Drill Set | Premium Step Bits | Thin sheet metal & clean deburring | M35 Cobalt / AlTiN coated | Amazon |
| STROTON Cobalt Set | Entry Cobalt Kit | First step up from HSS to cobalt | M35 Cobalt / 17 bits | Amazon |
| DEWALT DWA1181 HSS Set | General Purpose HSS | Wood, plastic & occasional mild steel | HSS / 135° split / 31° helix | Amazon |
| ss shovan Unibit Set | Budget Step Bits | Occasional sheet metal & HVAC work | M35 Cobalt / TiAlN / hex shank | Amazon |
In‑Depth Reviews
1. Drill America D/A29J-CO-PC 29 Piece M42 Cobalt Set
This is the set that professional fabricators and machinists reach for when drilling titanium, Inconel, or hardened alloy steel. The M42 cobalt grade, with approximately 8% cobalt content, delivers the highest red hardness in this roundup, permitting spindle speeds up to 30% faster than standard M2 HSS without softening the cutting edge. The gold oxide finish provides a dry lubricant effect that reduces friction during deep plunges into stainless steel.
The 29-piece index covers every 64th increment from 1/16″ to 1/2″, eliminating the guesswork when matching fastener drill sizes. The round case doubles as a cup-holder-friendly carrier or belt-hangable index, which is a practical touch for field service work. The 135° split point is standard here, ensuring immediate engagement on dome-headed bolts and smooth steel plate.
Users consistently report excellent chip formation and edge retention when paired with cutting oil at appropriate speeds. The main caveat is the premium investment — this is a specialist set for users who regularly encounter hard metals, not a casual homeowner kit. Small bits can arrive chipped if the case is mishandled in transit.
What works
- M42 grade handles hardened steel and titanium without softening
- Gold oxide reduces galling and extends per-hole life
- Compact index case designed for field portability
What doesn’t
- Smaller bits occasionally arrive with chipped tips
- Premium price limits it to serious metalworking use cases
2. toolant 108Pcs M35 Cobalt Drill Bit Set
This set bridges the gap between a small cobalt starter pack and a full industrial index, offering 108 bits with heavy duplication of the most-used sizes — 15 pieces each of 1/16″, 5/64″, 3/32″, and 1/8″. That depth is invaluable for mechanics and fabricators who burn through small bits on hardened fasteners or weld splatter. The M35 cobalt material and heat treatment deliver a lifespan reported by users as three times longer than standard HSS equivalents.
The 135° self-centering point is consistent across every bit in the index, producing clean, round holes without walking on I-beam flanges or automotive brackets. Real-world feedback from a mechanic drilling a dozen holes in thick I-beam steel for trailer lights with a single bit — without cutting oil — speaks to the material’s resilience. The flute design evacuates chips efficiently, reducing heat buildup during extended drilling in plate steel.
Storage is handled with individually sealed plastic bags inside a compact index case, which protects against moisture but makes the case markings slightly hard to read. The bits can feel brittle if laterally loaded in a hand drill, so using a drill press or maintaining alignment is recommended for the smaller diameters. For the volume and material quality, this represents strong value for serious DIYers and tradespeople.
What works
- Heavy duplication of small sizes reduces frequent replacements
- M35 cobalt cuts thick plate steel and hardened bolts with ease
- 135° split points start cleanly without center punching
What doesn’t
- Case markings are difficult to read quickly
- Small diameter bits can snap if misaligned in hand drills
3. EZARC M35 Cobalt Step Drill Bit Set (3pcs)
Step drill bits excel where you need multiple hole sizes in thin material without constantly swapping bits, and the EZARC set stands out with its C-profile triple-flute design. This geometry increases stability during the cut, reducing the deviation that causes oversized or oval holes in sheet metal. The M35 cobalt base maintains edge hardness, while the AlTiN coating — rated at 89 HRC — provides the highest heat and wear resistance in this category.
The three-bit range covers 1/8″ up to 7/8″, with Bit #1 handling common sizes for electrical enclosures and automotive panels. The 1/4″ hex shank eliminates slipping in keyless chucks and works directly with impact drivers, which is a practical convenience on jobsites. Users report drilling through 1/4″ thick steel with ease and that the bits stay sharp for dozens of holes when cutting oil is applied.
The main limitation is material thickness: EZARC specifies a maximum of 1/8″ for standard steel and 1mm for stainless steel. Pushing beyond that risks snapping the step, especially the larger diameters. A few users noted the largest bit fractured on its third hole in heavy material. This set is best reserved for thin-gauge applications like ductwork, brackets, and sheet metal fabrication.
What works
- Triple-flute C-profile cuts smoothly with reduced bit wander
- AlTiN coating resists high heat from continuous drilling
- Hex shank prevents slip in impact drivers and quick chucks
What doesn’t
- Not designed for steel thicker than 1/8″
- Large step diameter prone to snapping under heavy load
4. STROTON M35 Cobalt 17 Piece Drill Bit Set
The STROTON set is the entry point into cobalt steel without the premium sticker shock of M42 or massive multi-packs. The M35 grade with 5% cobalt content offers a noticeable upgrade over standard HSS when drilling into stainless steel, cast iron, or hardened bolts. Users report drilling eight half-inch holes through 1/4″ steel with a single bit and the edge remaining serviceable — a task that would typically dull a black oxide HSS bit well before completion.
The cutting edges are ground three times during manufacturing, producing a more consistent relief angle than cheaper single-grind bits. The 135° split point is present across all sizes, and the included sizes from 1/16″ to 1/2″ cover most common fastener and clearance hole requirements. The plastic storage case has tight clamps that hold each bit securely, and the brand backs the set with a visible warranty promise.
The notable weakness is brittleness in the smaller diameters — several users experienced breakage on bits under 3/16″ when drilling into thin metal studs, likely due to lateral flex. The manufacturer honored replacement in those cases, but it suggests these bits demand a steady feed and proper alignment. For the price, this set delivers genuine cobalt performance for users who want to step up from HSS without committing to a large kit.
What works
- M35 cobalt cuts stainless and cast iron significantly better than HSS
- Triple-ground cutting edges produce clean, consistent holes
- Compact case with secure bit retention for job site carry
What doesn’t
- Small bits (under 3/16″) prone to snapping in thin material
- Limited size range compared to larger index kits
5. DEWALT DWA1181 21 Piece High Speed Steel Drill Bit Set
The DEWALT DWA1181 is the quintessential general-purpose set for mixed-material drilling — wood, PVC, fiberglass, and occasional mild steel. It uses high-speed steel with a black oxide coating that resists corrosion and retains lubricant better than bare steel. The 31° helix is slightly less aggressive than a full parabolic flute, making it well-suited for deep hole drilling in wood without grabbing or overheating on the withdrawal stroke.
The 135° split point is a welcome inclusion at this tier, significantly reducing walking on slick surfaces compared to the standard 118° points found on many entry-level sets. Users consistently note that the bits produce round, accurate holes in wood and cut through drywall and plastic effortlessly. The set includes duplicate sizes for the most commonly lost or broken small bits (1/16″, 1/8″, 3/16″, 1/4″), which is a practical touch for ongoing projects.
The limitation is the HSS material — it will work on mild steel for a handful of holes, but the edge degrades quickly on stainless or hardened alloys. This is not a set for serious metalwork, but for the home user who needs one kit to handle framing, shelving, and light metal repairs, the balance of sharpness, storage, and price is hard to beat.
What works
- 135° split point eliminates walking on metal and tile
- 31° helix provides smooth chip ejection in deep wood holes
- Durable case keeps bits organized and protected
What doesn’t
- HSS dulls rapidly on hardened or stainless steel
- Not designed for high-volume metal drilling
6. ss shovan 3PCS M35 Cobalt Step Drill Bit Set
This three-piece step bit set brings M35 cobalt and TiAlN coating to a price point that undercuts most premium step bits. The sizes cover a practical range: Bit #1 handles 1/4″ to 1/2″ increments, Bit #2 offers finer steps between 1/4″ and 1/2″, and Bit #3 extends up to 7/8″. The 118° X-type opening design uses a spiral flute intended for chip clearance, though it lacks the stability of the triple-flute C-profile found on higher-end step bits.
HVAC technicians and DIYers working with sheet metal, aluminum, and copper report that these bits cut through steel surprisingly well for the cost. The TiAlN coating adds surface hardness that helps the edges survive contact with stainless steel up to 1mm thick. The 1/4″ hex shank is compatible with impact drivers and standard chucks, reducing the need for adapter collets.
The durability is decent for intermittent use — one user drilled about 20 holes in strong material before the top step lost its edge. The 118° point is less aggressive than the preferred 135° for steel, meaning the bit may require more downward pressure to engage. This set is best suited for light-gauge metal work where the lower entry cost matters more than industrial longevity.
What works
- M35 cobalt and TiAlN coating at a competitive price point
- Hex shank fits impact drivers without slipping
- Three-step range covers common sheet metal hole sizes
What doesn’t
- 118° point wanders more on steel than 135° split points
- Edge life limited on thicker or hardened materials
Hardware & Specs Guide
Cobalt Percentage: M35 vs M42
The number following the ‘M’ indicates cobalt content. M35 contains approximately 5% cobalt, offering a solid balance of toughness and heat resistance for general steel drilling. M42 contains around 8% cobalt, significantly increasing red hardness — the ability to stay hard at dulling temperatures — making it the better choice for hardened alloys and production environments where bit life directly affects job cost.
135° Split Point Geometry
Unlike a standard chisel point, a split point grinds a secondary notch into the tip, creating two cutting edges that meet at the center. This design allows the bit to bite into steel immediately on contact instead of skating across the surface. It eliminates the need for center-punching on most jobs and produces rounder holes with less runout at the entry point.
Step Drill Bit Limits
Step bits are optimized for thin materials — typically up to 1/8″ for standard steel and 1mm for stainless. Each step represents a specific diameter, and the bit cuts that diameter to a depth equal to the step height. Exceeding the material thickness causes the bit to cut with the full flute width instead of a single step, leading to chatter, oversized holes, or bit fracture. Always verify the maximum cutting depth per step before use.
Cutting Speed and Lubrication
Steel drilling generates significant heat at the cutting edge. Running bits at excessively high RPM causes the edge to soften rapidly, especially with HSS. General guidance for steel is 2000-3000 RPM for 1/8″ bits, dropping to 500-1000 RPM for 1/2″ bits. Cutting oil or a coolant spray reduces friction and flushes chips, extending bit life by a wide margin. Cobalt bits tolerate higher speeds but still benefit greatly from lubrication.
FAQ
Can I use a standard HSS bit for hardened steel?
Why does my bit keep walking on the steel surface?
What does the cobalt percentage actually do for drilling?
Can step drill bits handle thick steel plate?
Final Thoughts: The Verdict
For most users, the drill bit for steel winner is the toolant 108Pcs M35 Cobalt Set because it delivers professional-grade cutting performance, heavy duplication of worn sizes, and a 135° split point across the entire index at a reasonable investment. If you want maximum red hardness for hardened alloys and production work, grab the Drill America M42 Cobalt Set. And for thin-gauge sheet metal and multi-size convenience, nothing beats the EZARC AlTiN Step Drill Set.