Drilling through steel demands a bit that can endure extreme friction without losing its edge. Standard high-speed steel bits dull fast when they encounter hardened steel, stainless steel, or cast iron, leaving you with burned tips and oval holes. The wrong choice means wasted time, snapped bits, and ruined workpieces.
I’m Mo Maruf — the founder and writer behind The Tools Trunk. I spend my time analyzing metallurgy specs, coating technologies, and tip geometries to separate real industrial-grade bits from marketing hype.
This guide delivers nine hours of comparative research on cobalt and titanium-coated options so you can pick the right drill bits for steel without burning through your budget or your materials.
How To Choose The Best Drill Bits For Steel
Steel drilling is a battle of heat and hardness. The wrong bit material overheats instantly, while the wrong tip geometry skates across the surface. Here are the three specs that separate a clean hole from a ruined bit.
Material: Cobalt Content vs High-Speed Steel
Standard HSS bits (often labeled 4241 or M2) are adequate for mild steel and aluminum but soften rapidly when drilling stainless or hardened steel. M35 cobalt steel adds 5% cobalt to the alloy, raising the Rockwell hardness to around 68 HRC. This allows the cutting edge to retain its temper at higher temperatures, making it the baseline choice for any regular steel drilling work.
Tip Geometry: 135° Split Point is Non-Negotiable
A 118° conventional tip requires a center punch to prevent walking and needs higher downward force to bite in. A 135° split point self-centers instantly, reduces thrust by 30%, and produces smaller chips that evacuate easier. For steel specifically, always choose 135° split point bits — they dramatically reduce operator fatigue and bit breakage.
Coating: TiAlN vs Basic Titanium Nitride
Titanium Nitride (TiN) coating reduces friction and adds surface hardness, but breaks down around 600°C. Titanium Aluminum Nitride (TiAlN) forms a ceramic-like aluminum oxide layer at high temperatures, surviving up to 800°C. For repetitive drilling in stainless or hardened steel, TiAlN-coated bits last three to five times longer than uncoated or basic TiN bits.
Quick Comparison
On smaller screens, swipe sideways to see the full table.
| Model | Category | Best For | Key Spec | Amazon |
|---|---|---|---|---|
| Crosstar M35 Cobalt 21-Piece | Premium Cobalt | Thin stainless & titanium sheet metal | TiAlN coating, Pilot Point tip | Amazon |
| STROTON M35 Cobalt 17-Piece | Mid-Range Cobalt | General heavy steel & cast iron | 5% cobalt, 68 HRC hardness | Amazon |
| VEVOR Cobalt 29-Piece | Premium Cobalt | Maximum size variety in cobalt | 29 sizes, 135° split point | Amazon |
| GMTOOLS Titanium HSS 230-Piece | Budget HSS | High-volume light metal & wood drilling | 230 pieces, 135° split point | Amazon |
| GDLIN Titanium HSS 230-Piece | Budget HSS | Entry-level mixed material drilling | 118° tip, straight shank | Amazon |
In‑Depth Reviews
1. Crosstar M35 Cobalt Drill Bit Set 21-Piece
This set is uniquely engineered for thin, hard, and gummy metals — stainless steel sheet, titanium, and hardened panels that cause standard bits to skate and work-harden the surface. The M35 cobalt core provides the hot hardness needed to resist edge softening, while the TiAlN nano-coating withstands friction temperatures exceeding 800°C, a critical advantage over basic TiN-coated bits.
The self-centering Pilot Point tip eliminates bit walk on curved or reflective surfaces, and the 135° split point allows faster penetration with less downforce. Sizes from 1/16″ to 1/2″ include duplicates of the five smallest diameters, which are the most likely to snap under hard use. The hex shank prevents chuck slippage, and the robust compartmentalized case with laser-etched labels keeps every bit organized and easy to identify.
Users consistently report clean holes with minimal exit burrs on stainless steel, and the 90-day satisfaction guarantee provides a safety net if any bit fails prematurely. The only catch is that the 1/16″ to 1/8″ bits use a standard tip rather than the bullet point design found on larger sizes, so start with light pressure on those smaller diameters.
What works
- TiAlN coating handles extreme heat without degrading
- Pilot Point tip starts dead center without a punch
- Hex shank eliminates chuck slippage under torque
What doesn’t
- Small bits (1/16″ to 1/8″) lack the bullet point geometry
- Storage case build quality feels mediocre for the price tier
- Some users report brittleness on very hard steel
2. STROTON M35 Cobalt Drill Bit Set 17-Piece
The STROTON set delivers the essential sweet spot of 5% cobalt content, 68 HRC hardness, and a triple-ground cutting edge that cleaves through stainless steel, hardened steel, and cast iron with long, continuous iron chips rather than grinding dust. The 135° split point ensures immediate bite and self-centering, so you don’t need to pre-punch harder materials.
With 17 pieces covering 1/16″ to 1/2″, including duplicates of the most common small sizes, this kit avoids the bulk of 200+ piece sets while focusing on the diameters that matter for real metalwork. The cutting edge geometry is ground three times at the factory, generating a sharper edge than single-ground bits, which translates directly to faster feed rates and lower torque demand on your drill.
The plastic storage case has tight bit clamps that keep everything secure in a toolbag, and the manufacturer offers a free replacement warranty that several customers have successfully used. The only common complaint involves brittleness in bits under 3/16″ when used on thin metal studs — but that’s a characteristic of any hardened cobalt bit under lateral stress, not a defect specific to this brand.
What works
- Triple-ground edge stays sharp through heavy use on steel
- 135° split point eliminates walking on hard surfaces
- Free replacement warranty adds long-term value
What doesn’t
- Small bits under 3/16″ can snap with lateral pressure
- No TiAlN coating — relies on bare cobalt hardness
- Limited to 17 sizes; no fractional odd sizes included
3. VEVOR Cobalt Drill Bit Set 29-Piece
VEVOR’s 29-piece offering is the most comprehensive cobalt set in this lineup, spanning 1/16″ to 1/2″ with an extensive range of mid-sizes that conventional 21-piece sets skip. The M35 high-speed steel with 5% cobalt provides the same 135° split point advantage, and the black oxide finish adds a layer of corrosion resistance that bare cobalt lacks — useful if your bits sit in a humid shop environment.
The storage case stands out as one of the best in this test group, with secure bit holders and clearly labeled slots that make size selection quick on the job. Users report that the set holds up well in mild steel, aluminum, and wood, but like all cobalt bits, these require dead-straight drilling alignment — any sideward pressure during the cut can snap the bit, especially in the smaller diameters.
The weight of 3.53 pounds reflects the all-cobalt construction and the heavy-duty case, making this kit less portable than a pouch but better suited for a workshop drawer or drill press station. Several DIYers with VEVOR experience report consistent quality across the brand’s tool lineup, and the price per bit in this set makes it a strong value for anyone who needs fractional sizes beyond the standard 1/16, 1/8, 1/4, 3/8 increments.
What works
- Widest size range among cobalt bits in this guide
- Black oxide finish resists rust in damp conditions
- Sturdy, well-organized storage case
What doesn’t
- Fragile under side loading — requires straight drilling
- No TiAlN coating limits heat tolerance on stainless
- Brand reputation still building in tool community
4. GMTOOLS Titanium HSS Drill Bit Set 230-Piece
GMTOOLS delivers a massive 230-piece set built from 4241 high-speed steel with a titanium coating and a 135° split point — the same tip angle found on premium cobalt bits. The hex shank design prevents the bit from spinning in the chuck, a real advantage when drilling steel with a standard three-jaw chuck that might not grip round shanks tightly enough.
While the HSS substrate lacks the thermal hardness of M35 cobalt, the titanium coating extends the usable life enough for mild steel, aluminum alloy, copper, and wood. This set is best suited for high-volume drilling in softer metals where cobalt’s extra cost isn’t justified. The included sizes are heavily weighted toward small diameters — 40 pieces of 1/16″ and 38 pieces of 5/64″ — ideal for electrical panel work or thin metal fabrication.
The storage case has been noted as less durable than premium options, and bits can arrive mixed up in shipping. Customer service responsiveness has also drawn mixed feedback, with one user reporting the company refused a replacement for a broken 9/64″ bit. For the sheer volume and the 135° geometry, however, this remains a solid entry-level option for mixed-material drilling.
What works
- Hex shank prevents chuck slippage during drilling
- High bit count with duplicates of common small sizes
- 135° split point at a budget-friendly price point
What doesn’t
- HSS substrate can’t match cobalt on harder steels
- Case quality is mediocre; bits may arrive jumbled
- Customer service reported as uncooperative
5. GDLIN Titanium HSS Drill Bit Set 230-Piece
The GDLIN set uses 118° conventional tips rather than the 135° split point, which is a meaningful distinction for steel drilling. The 118° angle requires a center punch to maintain alignment and creates more walking on smooth steel surfaces, so beginners will need to pre-mark every hole. The titanium-coated HSS material is adequate for carbon steel plates, soft metals, aluminum, wood, and plastic — but not for hardened or stainless steel.
With 230 pieces spanning 3/64″ to 1/2″, the set includes heavy duplicates of the smallest sizes, which makes it practical for production environments where small bits wear out fast. The straight shank design is standard and works with any drill chuck, though it offers no anti-slip advantage over a hex shank. The double U-shaped flute is designed for efficient chip evacuation in wood and plastic, but the spiral flute profile also handles metal chips adequately at slower speeds.
One verified user reported that two bits deformed like wax when attempting to drill a 55-gallon steel drum — a clear indication that this set is not intended for heavy-gauge or hardened steel. For light-duty drilling in mild steel, aluminum, and general workshop materials, the GDLIN set provides an immense quantity of bits at an entry-level investment, with the caveat that you must match the bit to the material.
What works
- Extremely high bit count with many duplicate small sizes
- Well-organized case with size index for quick access
- Double U-shaped groove clears wood and plastic chips well
What doesn’t
- 118° tip requires center punch; walks on smooth steel
- HSS material deforms on hardened or stainless steel
- Self-centering claim is exaggerated — expect wandering
Hardware & Specs Guide
Cobalt Content Percentage
M35 cobalt steel contains exactly 5% cobalt by weight, raising the material’s red hardness — its ability to stay sharp at high temperatures — far beyond standard M2 HSS. Bits with 5% cobalt (like the STROTON, Crosstar, and VEVOR sets) can maintain cutting integrity up to approximately 600°C, whereas standard HSS begins softening around 400°C. For drilling through stainless, hardened steel, or cast iron, 5% cobalt is the minimum viable content.
TiAlN vs TiN Coating
Titanium Aluminum Nitride (TiAlN) coating, found on the Crosstar set, forms an aluminum oxide layer at high temperatures that acts as a thermal barrier. This coating survives up to 800°C, making it ideal for continuous drilling on stainless steel. Basic Titanium Nitride (TiN) coating, used on the GMTOOLS and GDLIN sets, provides surface hardness and friction reduction but breaks down around 600°C — still helpful for mild steel but not sufficient for prolonged hard steel contact.
FAQ
Can I use standard HSS bits for hardened steel or stainless steel?
What is the practical difference between a 118° tip and a 135° split point?
Why do some cobalt bits snap so easily on thin metal?
How often should I apply cutting oil when drilling steel?
Final Thoughts: The Verdict
For most users, the drill bits for steel winner is the STROTON M35 Cobalt 17-Piece Set because it delivers proven cobalt hardness, a triple-ground edge, and a 135° split point at a price that makes sense for both serious DIYers and light professional use. If you regularly work with thin stainless sheet or titanium and need the best heat resistance, grab the Crosstar M35 Cobalt 21-Piece Set with its TiAlN coating and self-centering Pilot Point. And for maximum size variety in cobalt without paying per-bit premiums, nothing beats the VEVOR Cobalt 29-Piece Set.