When you need a clean hole through stainless, cast iron, or hardened steel, the geometry of the cutting edge and the alloy of the steel blank determine success or failure before you ever pull the trigger. The wrong bit overheats, dulls fast, and leaves a ragged opening you’ll have to ream or scrap entirely.
I’m Mohammad Maruf — the founder and writer behind Gardening Beyond. For this guide, I pored through hundreds of verified owner reports and cross-referenced metallurgical specifications on M2 HSS, M35 cobalt, titanium nitride coatings, and split-point angles to see which bits actually survive contact with abrasive metal surfaces over multiple holes.
The real difference between a frustrating drilling session and a smooth one comes down to three factors: the steel type, the point geometry, and the coating. Whether you are punching through a mild steel bracket or a stainless steel plate, finding the right bit for drilling metal means choosing a tool that can handle friction without losing its edge.
How To Choose The Best Bit For Drilling Metal
Selecting a metal drill bit is a metallurgy decision first and a price decision second. The material of the bit must be harder than the workpiece, and the point geometry must control the cutting action. Below are the three pillars to evaluate before you buy.
Steel Alloy: The Difference Between HSS, M2, and M35 Cobalt
Standard HSS bits work fine on mild steel and aluminum but soften quickly when drilling stainless or hardened alloys. M2 HSS adds tungsten and molybdenum for roughly 50 percent more wear resistance. M35 cobalt steel contains 5 percent cobalt, boosting red hardness so the bit maintains its edge even when friction generates extreme heat at the cutting lip. For frequent work on stainless steel or cast iron, M35 cobalt is the baseline you should not compromise on.
Point Geometry: Why 135-Degree Split Points Matter
A conventional 118-degree point tends to walk or skate across a smooth metal surface before it engages. The 135-degree split point features a self-centering web that bites into the workpiece immediately, reducing the need for a center punch on most materials. This geometry also produces shorter, more manageable chips that clear the flute more easily, lowering the risk of binding in deeper holes.
Coatings and Surface Treatments
Titanium nitride (TiN) and black oxide coatings reduce friction and improve lubricity during drilling. TiN is excellent for production work where heat buildup is constant. Black oxide retains cutting oil better on the surface, which helps in manual drilling scenarios where consistent lubrication is harder to maintain. Uncoated cobalt bits can still outperform coated HSS bits on hard metals because the base alloy matters more than the surface layer.
Quick Comparison
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| Model | Category | Best For | Key Spec | Amazon |
|---|---|---|---|---|
| Jerax Tools Step Drill Bit | Step Drill | Multi-size holes in sheet metal | 12 marked steps up to 7/8″ | Amazon |
| RCINDUS 15pc Cobalt Set | Jobber Twist | Hardened metal and stainless steel | M35 cobalt, 5% Co | Amazon |
| WildBossy M35 20pc Set | Jobber Twist | General metal drilling with range | 67 HRC hardness rating | Amazon |
| Milwaukee Shockwave TiN Set | Jobber Twist | Production drilling in alloy steels | 3-flute, TiN coating | Amazon |
| CaRoller 29pc Black & Gold | Jobber Twist | Mild steel and aluminum work | 29-piece, 135° split point | Amazon |
In‑Depth Reviews
1. Jerax Tools Step Drill Bit
This step drill bit from Jerax Tools uses M2 high-speed steel with an additional vacuum heat treatment and nitride surface hardening, giving it a significant durability advantage over generic step bits. The polished steps include laser-etched size markings from 3/16 up to 7/8 inch, so you can see the target diameter without stopping to measure mid-drill. Users consistently report clean holes through aluminum, mild steel, and even stainless steel up to 12-gauge thickness when appropriate pressure is applied.
The straight grooved double-fluted design clears chips efficiently, which is critical when drilling deeper steps in sheet metal where clogging can stall the cut. Multiple verified reviews note that this single bit replaces the need for a full kit of individual twist bits for common electrical enclosure and automotive panel work. The protective plastic case keeps the stepped edges from knocking against other tools.
Where this bit truly differentiates itself is in stainless steel performance without a pilot hole. Owners report that the M2 alloy with nitride treatment stays sharp through multiple stainless penetrations that would dull a standard HSS step bit in a single pass. For anyone drilling several different hole sizes in metal panels, this is the most efficient single tool you can keep in your pouch.
What works
- Marked steps let you dial in exact hole size without stopping
- Nitride-hardened M2 steel cuts stainless steel without a pilot hole
- Double flute clears chips fast in thicker material
What doesn’t
- Limited to hole sizes within the step range; no small fractional bits
- Requires steady pressure on harder alloys to avoid chatter
2. Milwaukee 48-89-4630 Shockwave TiN Kit
Milwaukee’s Shockwave line uses a titanium nitride coating over the steel substrate to reduce friction and extend cutting life in production drilling scenarios. The 15-piece kit covers the most commonly used sizes for metal fabrication and general repair work. The 135-degree split point is standard here, ensuring the bit engages the surface without skating, even on rounded or smooth steel surfaces.
A standout feature is the three-flute design on some of the larger bits, which provides additional chip evacuation compared to traditional two-flute geometry. Owners report that these bits maintain their edge through dozens of holes in mild steel and alloy steel when used with proper cutting speed and lubrication. The plastic locking case keeps the bits organized and prevents the TiN coating from being scratched by adjacent tools.
Some users noted that the smaller bits could be slightly longer for deeper penetration through thick lumber when drilling pilot holes, but for pure metal-to-metal drilling, the length is appropriate. The biggest strength of this set is consistency: every bit in the kit performs at the same high level, meaning you can reach for any size and expect the same clean cut without experimenting with feed pressure.
What works
- TiN coating significantly reduces heat buildup during prolonged drilling
- Three-flute geometry on larger sizes improves chip clearance
- Consistent quality across the entire set with no weak sizes
What doesn’t
- Smaller bits are relatively short for deep wood pilot holes
- Premium price point compared to unbranded cobalt sets
3. RCINDUS 15pc Cobalt Drill Bit Set
This RCINDUS set delivers fifteen identical 1/4-inch M35 cobalt bits, which is an unusual but highly practical configuration for anyone who frequently drills out stripped screws or needs a dedicated bit for repetitive hardened-metal work. The M35 alloy with 5 percent cobalt gives these bits the red hardness to handle stainless steel, cast iron, and other abrasive materials without annealing the cutting edge. The 135-degree split point ensures immediate engagement on smooth surfaces.
Factory-direct quality control keeps diameter accuracy within minus 0.03mm, which is tighter than many consumer-grade drill bits. Multiple verified reviews confirm that a single bit survived drilling out roughly 25 stripped screw heads before showing any signs of dulling. The uncoated finish means the bit relies entirely on its metallurgical composition rather than a surface layer, making resharpening simpler when the edge eventually wears.
For the DIYer who works primarily with hardened steel or stainless, having a fifteen-pack of identical 1/4-inch bits means you never have to stop mid-project to hunt for a fresh bit. The included plastic case keeps the bits separated and protected. If you need a range of sizes rather than a single size in quantity, this configuration may feel limiting, but for targeted heavy-duty use, it is hard to beat.
What works
- M35 cobalt alloy handles hardened steel and stainless without overheating
- Fifteen identical bits give you a large consumable supply for repetitive drilling
- Split point eliminates walking on smooth metal surfaces
What doesn’t
- Only one size available; no variety for different hole diameters
- Uncoated surface requires more careful lubrication during drilling
4. WildBossy M35 Cobalt 20pc Set
The WildBossy 20-piece set spans from 1/16 to 1/2 inch, giving you a broad range of jobber-length cobalt bits for a mid-range investment. The M35 cobalt steel is rated at 67 Rockwell hardness, which is competitive with more expensive brands. The 135-degree split point is paired with a titanium surface treatment and a three-flat shank design that prevents the bit from spinning in the chuck under heavy torque.
Owner experiences are split between excellent performance on thin stainless steel and some inconsistency in hardness across the set. One verified user drilled through stainless with ease at slow speed, while another reported that a few bits in the set were dull from the factory or snapped during normal use. This variance is worth noting if you expect every bit in the kit to perform identically out of the box.
For the price point, the overall value is strong for someone who needs a wide size range and wants cobalt capability without stepping up to premium-brand pricing. The plastic storage case is basic but functional. If you are willing to check each bit for edge quality before use and discard any outliers, this set covers most home workshop metal drilling needs without breaking your tool budget.
What works
- Wide size range from 1/16 to 1/2 inch covers most common metal drilling tasks
- Three-flat shank prevents chuck slippage under heavy load
- Cobalt alloy with titanium coating handles thin stainless steel effectively
What doesn’t
- Inconsistent hardness across some bits in the set
- Occasional reports of bits arriving dull or snapping on first use
5. CaRoller 29pc Black & Gold Drill Bit Set
The CaRoller 29-piece set uses W4 high-speed steel with a black oxide finish and an amber coating, offering a huge size selection at a budget-friendly entry point. With sizes from 1/16 to 1/2 inch in 64th-inch increments, this set is one of the most complete fractional kits available for the price. The 135-degree split point helps with self-centering on metal surfaces, reducing the need for center punching on mild steel.
Owner feedback shows that these bits perform very well on mild steel and aluminum. One verified user drilled 30 holes into a steel I-beam with a single bit before noticing significant wear, which is impressive for an HSS bit at this price. The black oxide finish helps retain cutting oil on the surface, improving lubrication during drilling. The plastic case has a secure latch but some users reported it expanding slightly in warm conditions.
Where this set falls short is on hardened metals like stainless steel. Multiple reviews indicate that while the bits can cut stainless with slow speed and oil, they dull faster than cobalt alternatives. For the home user who works primarily with mild steel, aluminum, and wood, this set delivers tremendous value. For regular stainless work, you will want to supplement with dedicated cobalt bits.
What works
- Exceptional size variety with 29 pieces covering 64th-inch increments
- Black oxide finish holds cutting oil for better lubrication
- Surprisingly durable on mild steel; one bit drilled 30 I-beam holes
What doesn’t
- HSS base alloy dulls faster on stainless and hardened metals
- Plastic case can warp or expand in warm environments
Hardware & Specs Guide
M35 vs M2 HSS Steel Alloys
The primary difference is cobalt content. M35 high-speed steel contains 5 percent cobalt, which boosts its red hardness—the ability to stay hard at elevated cutting temperatures. M2 HSS lacks cobalt but uses higher tungsten and molybdenum levels for good general-purpose wear resistance. For stainless steel and hardened alloys, choose M35. For aluminum and mild steel, M2 is sufficient.
Split Point vs Conventional Point
A conventional 118-degree point has a straight chisel edge that can skate on metal. A 135-degree split point has a thinned web that creates two cutting edges meeting at the center, allowing the bit to self-center and start cutting immediately. Split points eliminate the need for center punching on most materials and reduce the force required to initiate the cut.
Step Drill Bit Design Benefits
Step bits feature a conical shape with graduated diameters, allowing a single bit to drill multiple hole sizes without changing tools. The stepped design distributes cutting forces across a wider area, reducing chatter in thin sheet metal. Marked step bits let you stop at the exact diameter, making them ideal for electrical enclosures and automotive panel work.
Flute Count and Chip Evacuation
Two-flute twist bits are standard and work well for most drilling tasks. Three-flute designs, found on some premium bits like the Milwaukee Shockwave, provide additional chip clearance and reduce binding in deeper holes. More flutes mean less space for chips to travel, so three-flute bits work best when drilling with consistent pecking action to break chips.
FAQ
Can I use a standard wood drill bit on metal?
What speed should I use when drilling metal?
Is cobalt better than titanium for metal drilling?
How do I prevent a drill bit from walking on metal?
Final Thoughts: The Verdict
For most metal drilling tasks, the best bit for drilling metal is the Jerax Tools Step Drill Bit because its M2 HSS construction with nitride hardening delivers clean holes across multiple diameters in stainless and mild steel without needing a full bit set. If you want a production-ready cobalt set that handles hardened steel with ease, grab the RCINDUS 15pc Cobalt Drill Bit Set. And for a broad size range at a budget-friendly entry point, nothing beats the CaRoller 29pc Black & Gold Set for mild steel and aluminum work.